Gas cleaning process and equipment therefor

ABSTRACT

The invention relates to equipment for use in the removal of relatively fine particulates from a first substance, using a second substance. The equipment includes a static, co-current contacting mixer section, having a plurality of stages defining a flow path, with a flow profile, for the first and the second substance, at least some of the stages being shaped to define a substantially curved flow path having an effective centre of curvature located to one side of the flow path, and wherein each adjacent stage has a centre of curvature on an opposite side of the flow path to provide a point of inflexion between adjacent stages and whereby, as the substances flow through the reactor between the adjacent stages, particles present in the first substance migrate through the second substance, first in one direction and then in a substantially opposite direction to promote interphasic interaction between the first and the second substance, the flow path characterised in being provided with an edge formation between at least two adjacent stages towards the point of inflexion so as to enhance the launch of the second substance on the outside of the curved flow path of one stage at relatively high velocity from the edge formation to the inside of the curved flow path of the adjacent stage, thus increasing the contact between the first and the second substances. The equipment also includes a cyclonic section and a spinner section. The invention also relates to a method for the removal of relatively fine particulates from a gas stream, using a scrubbing fluid, as well as a plastic composite material for the manufacture of the equipment.

TECHNICAL FIELD

This invention relates to a gas cleaning process and equipment therefor.

More particularly but not exclusively, the invention relates to theremoval of relatively fine particulates from a gas stream, using ascrubbing fluid, and the subsequent separation of the gas and thescrubbing fluid, as well as equipment therefor.

This invention further relates to plastic and abrasion resistantcomposite materials for the manufacture of the equipment for the removalof the particulates from the gas stream and the subsequent separation ofthe gas and the scrubbing fluid.

BACKGROUND ART

The removal of relatively fine particulates from a gas stream, using ascrubbing fluid, together with the subsequent separation of the gas andthe scrubbing fluid, is well known, and is often carried out by means ofa so-called wet scrubbing process.

More particularly, the removal of relatively fine particulates from agas stream, using a scrubbing fluid, and the subsequent separation ofthe gas and the scrubbing fluid, is applied in the treatment of the hotoff-gases from a Sinter Process such as that which forms part of many ofthe modern iron making processes.

The off-gases from the Sinter Process typically have a temperature ofaround 150° C., with a short duration maximum of around 180° C. to 200°C. The gases contain the products of a carbon fuelled combustion processwith a relatively large amount of excess air. The gases also containdust, products of incomplete combustion (including dibenzo-furans, PCB'sand related compounds), acid gases (derived from sulphur and otherimpurities in the feed stocks) and condensed fumes. These fumestypically contain condensed alkali and other metal salts (usuallychlorides) and condensed silica compounds with other similarly sizedfine particulates resulting from decrepitation and other processes thatoccur within the sintering process.

As a result of the processes that occur, the total dust load isessentially made up of two distinctly sized groups, a relatively coarsefraction and a relatively fine fraction. The coarse fraction is usuallyextracted from the off gases using cyclonic or other equivalentseparators and this is usually done between the sinter process and themain extraction fans which are used to draw the combustion air throughthe sinter process. Removal of this coarse dust upstream of these fansensures minimum wear on these fans.

Downstream of the fans, the fine dust and other contaminants have to beremoved before the off-gases can be discharged to atmosphere. Currenttechnologies for this utilise bag filters, electrostatic precipitatorsand wet electrostatic precipitators.

In many instances, however, the proportion of alkali salts (potassiumand sodium salts) causes the dust that is to be removed, unsuitable forbag filters and normal electrostatic precipitators, leaving wetelectrostatic precipitators as the only existing technology option whichis capable of meeting the current requirements regarding final dustconcentrations.

Normal wet scrubbing processes and related systems are typically able toremove particles at relatively high efficiencies down to particle sizesof around 3 to 5 microns. A disadvantage of these wet scrubbingprocesses and systems is however their inability to achieve removalefficiencies of above 90% of particle sizes of less than 0.05 micron. Afurther disadvantage is the relative large bulk of the known wetscrubbing systems. Another disadvantage of the known wet scrubbingsystems is the relatively large floor area required by those systemsthat are capable of achieving removal efficiencies of above 90% ofparticle sizes of less than 0.05 micron, such as the conventionalElectrostatic Precipitator (“ESP”) or the bag house installation.

An additional disadvantage of the typical primary equipment, orcomponents of the assemblies, or so-called packs of components used inthe known wet scrubbing systems is the relative difficulty with whichthey are moulded or cast, using low cost plastics, resins and reinforcedplastics or resins (with or without abrasion inhibiting fillers). Afurther disadvantage of the equipment and components is the relativedifficulty with which they are assembled and maintained, typicallyrequiring the use of specialist tools and/or support services.

The influence of the degree of mixing, and hence the contactaccomplished, during the multi-phase interaction in the scrubbingprocess on the efficiencies obtained with a gas scrubbing process andthe associated equipment is also well known. The use of equipment forintensifying the mixing and contacting during the multi-phaseinteraction is therefore common practice.

High intensity mixing and contacting is for example accomplished in theso-called Multiphase Staged Passive Reactor (“MSPR”), with its smoothlycontoured design, substantially as described in U.S. Pat. No. 5,741,466and French Patent No 1.461.788.

The MSPR, as described in the above French Patent, is a static,co-current contacting device for contacting a flow of gas with atypically smaller volumetric flow of liquid, mixture of liquids orslurry. The device is typically used for the purposes of enhancing massand/or heat transfer in, the removal of fine particulates from, and thecreation and dispersion of fine liquid or slurry droplets into a gasstream. The mass transfer typically includes evaporation or partialevaporation of the liquid, the partial or complete condensation,dissolution or reaction of gaseous or vapour components within the gasonto, into or with the liquid(s) or slurry, or the partial or completeremoval of a component within the liquid, mixture of liquids or slurryinto the gas stream.

The MSPR, as described in the above U.S. patent, has no moving parts,and is typically used for producing interphasic interaction of a firstsubstance in a liquid phase with a second substance in a non-miscibleliquid phase, a solid phase or a gaseous phase, wherein the phases ofthe first and the second substances respectively are characterised bydifferent relative densities. This MSRP typically comprises a pluralityof stages defining a flow path for the first and the second substances,each stage being shaped to define a substantially curved flow pathhaving a centre of curvature located to one side of the flow path, andwherein adjacent stages have a respective centre of curvature onopposite sides of the flow path whereby, as the substances flow throughthe reactor, particles of the second substance are forced to migratethrough the first substance, first in one direction and then insubstantially in the opposite direction to promote interphasicinteraction.

The MSPR has characteristically a relatively smoothly profiled andconstant annular flow passage, so that when applied in gas scrubbing,the scrubbing fluid that collides with the wall of the profile tends toaccumulate on the inside curve of each bend in the profile and then“drips off” as a semi continuous flow of droplets. This flow of dropletspulls away from the accumulated layer of fluid as a result of inducedturbulence from the gas as it flows around the inside of the bend andcentrifugal forces resulting from the velocity of the fluid over thesurface of the flow passage. In general, not all of the scrubbing fluidwill come off the surface of the profile, leaving a significantproportion to flow over the subsequent surface. As a result, this partof the scrubbing fluid will not present itself to the bulk of the dustin the gas flow. Also, for a given gas velocity, the droplets that doleave will be relatively large droplets, all of which do not leave fromthe same point on the inside radius. Some droplets also tend to bereleased within the shadow of a droplet, that was released a fewmillimetres earlier, rather than to fill the gaps between previouslyand/or simultaneously released droplets. As a result, a relatively lowproportion of the total gas flow will be traversed by the droplets thatare released, than would be the case if the same number of drops werereleased uniformly around the perimeter.

In addition, much of the scrubbing fluid that is released will bereleased from relatively far around the inside of the bend. On theinside of the bend, because of turbulence within the gas on the insideof the bend, the shear forces from the high velocity gas will not all bein the direction of the bulk flow. As a result, there will be a reducedvelocity input from the gas into the surface layer of the scrubbingfluid on this part of the surface of the flow profile. This, togetherwith viscous drag from the stationary wall of the flow profile withinthe film of scrubbing fluid, will cause the film velocity at the releaseof the droplet to be significantly lower than that of the film velocityupstream of the inside radius.

This reduced velocity and the orientation of this velocity with regardto the subsequent flow profile, results in specific disadvantages,including a relatively smaller number of larger droplets, therebypresenting a substantially reduced droplet surface area; and lack ofpenetration in that the majority of the droplets do not penetraterelatively far into the gas flow before the following bend causes themto move back towards the wall again as a result of both centrifugalaction and inertia.

The resultant substantially reduced droplet surface area causes arelatively poor scrubbing efficiency per unit volume of scrubbing fluidthat is released from the surface of the flow profile.

The lack of penetration causes a tendency for scrubbing fluid on oneside of the flow profile to scrub the gas on that side of the profileonly and for the fluid on the other side to scrub the gas on the otherside only, with relatively little intermixing of the two flows ofscrubbing fluid.

An additional disadvantage of partial contact of the gas with thescrubbing fluid, is that each time the scrubbing fluid leaves the solidsurface of the walls of the flow profile, the gas flow tends toaccelerate the droplets up to the gas velocity in that area, causingmuch of this additional velocity energy to be lost when the dropletsre-combine with the film of fluid on the wall. The energy loss per unitof dust or fine droplet removal, per unit of gas scrubbing, becomesparticularly significant when the droplets do not contact much of thetotal gas flow.

A related disadvantage of the MSPR is therefore its inability to retainthe relative velocities of the gas and fluid flow through the flowprofile, allowing the decline in relative velocities to reduce theability of the scrubbing fluid droplets to remove fine dust and otherparticulates.

A further disadvantage of the MSPR is the lack of overall wear andchemical resistance of the material used for the manufacture of the MSPRas well as its ability to with stand environments of high impact,abrasion, corrosion and temperature demands such as those present withthe scrubbing of the hot off-gases from the Sinter and other furnacerelated processes.

OBJECT OF THE INVENTION

It is accordingly a first object of the present invention to provide arelatively inexpensive, but effective method for the removal ofrelatively fine particulates from a gas stream, using a scrubbing fluid,and the subsequent separation of the gas and the scrubbing fluid, suchas that required for the scrubbing of the hot off-gases from the Sinterand other furnace related processes.

It is a second object of the present invention to provide relativelyinexpensive, but effective, equipment for use in the removal of theparticulates from the gas stream, and the subsequent separation of thegas and the scrubbing fluid.

It is a third object of the present invention to provide relativelyinexpensive, but effective, plastic composite materials for themanufacture of the above equipment for the removal of the particulatesfrom the gas stream and the subsequent separation of the gas and thescrubbing fluid.

DISCLOSURE OF THE INVENTION

According to a first aspect of the invention there is provided equipmentfor use in the removal of relatively fine particulates from a firstsubstance, using a second substance, the equipment including a static,co-current contacting mixer section having a plurality of stagesdefining a flow path, with a flow profile, for the first and the secondsubstance, at least some of the stages being configured and dimensionedto define a substantially curved flow path having an effective centre ofcurvature located to one side of the flow path, and wherein eachadjacent stage has a centre of curvature on an opposite side of the flowpath to provide a point of inflexion between adjacent stages andwhereby, as the substances flow through the mixer section between theadjacent stages, particles present in the first substance migratethrough the second substance, first in one direction and then in asubstantially opposite direction to promote interphasic interactionbetween the first and the second substance, the flow path characterisedin being provided with an edge formation between at least two adjacentstages towards the point of inflexion so as to enhance the launch of thesecond substance on the outside of the curved flow path of one stage atrelatively high velocity from the edge formation to the inside of thecurved flow path of the adjacent stage, thus increasing the contactbetween the first and the second substances.

The first substance may be a gas and the second substance may be ascrubbing fluid.

The edge formation may be stepped, and is preferably provided with asubstantially perpendicular face relative to the edge formation toenhance the launch of the scrubbing fluid. The perpendicular face may beprovided with a slight taper to facilitate mould release when cast.

The stepped edge formation may be provided with a ledge subsequent tothe step to provide a first and a second step, the first and the secondstep preferably being arranged so as to encourage a small back eddy ofgas immediately beneath the first step that deflects any downwardsdribble of scrubbing fluid around the stepped edge back up into theunderside of the main fluid flow as it leaves the first step so as tomaximize the contact between the launched scrubbing fluid and the gas.

Each stepped edge may have a fillet radius to ensure maximum effect fromthe swirl and scouring action from the back eddy, which is encouragedwithin the stepped edge. The step may have a similar depth and widthrelative to the stepped edge, preferably of between 0.5 and 2.5% of theoutside diameter of an annulus.

The mixer section may be provided with an edge formation towards eachpoint of inflexion. The flow path is preferably configured anddimensioned to orientate both the angle and the position of each launchwith respect to the subsequent shape of the flow profile and thecontrolled change in direction of the flow profile so as to catch themaximum of the scrubbing fluid that are launched at a landing zone onthe opposite side of the flow profile before a subsequent launch, thusachieving maximum scrubbing effect from all scrubbing fluid.

The flow path may have a flow profile that is configured anddimensioned, with the step towards the start of each inside radius, suchthat the position of launch of effectively all the scrubbing fluid istowards the beginning of each inside curve so as to maximize the contactbetween the launched fluid and the gas. The flow path may have has aflow profile that is configured and dimensioned such that the scrubbingfluid leaves at the point of launch as a substantially single, flatlayer of fluid, thereby ensuring that the minimum of droplets arereleased within the shadow of droplets that left prior thereto so as tomaximize the contact between the launched scrubbing fluid and the gas.The flow path may have a flow profile that is configured and dimensionedsuch that the bulk of the scrubbing fluid reaches the far side of theflow profile before the scrubbing fluid on that side is released at theposition of launch towards the beginning of the next bend so as tomaximize the contact between the launched scrubbing fluid and the gas.The flow path may have a flow profile that is configured and dimensionedsuch that, by the angle of the lead up to that step and the introductionof substantially axially orientated straight sections to the flowprofiles, the scrubbing fluid, when reaching the opposite side wall,arrives at an angle of approach which approaches zero degrees so as tomaximise the recovery of the energy of the droplets within the surfacefilm and therefore to minimise abrasion at the landing zone. The flowpath may have a flow profile that is configured and dimensioned, by theintroduction of substantially axially orientated straight sections tothe flow profiles, so that the distance from the landing zone to thesubsequent launching point is minimized so as to minimise the subsequenteffects of viscous drag on the landing velocity of the scrubbing fluid.

The flow path may have an increased launch angle of between about 3° and10° relative to that which is used for the outer annulus. The flow pathmay be configured and dimensioned to provide an increased gas velocitydown the inner annulus of between about 5 and 25% relative to that downthe outer annulus.

The flow path may have a flow profile that is characterised in that thebend that gathers the scrubbing fluid ready for launching into the outerannulus is configured and dimensioned such that the scrubbing fluiddroplet impingement and film velocity on this bend and at the subsequentlaunch point are no more severe than for that at the equivalent point inthe outer annulus.

The flow path may have a flow profile that is configured and dimensionedsuch that the section of the flow profile leading from each innerannular zone to the respective following outer annular zone optimisesrecovery of the extra velocity energy in the inner annulus area back topressure energy at the outer annulus. Preferably, the flow path has aflow profile downstream of the landing zone for the bulk of the dropletswherein the flow area increases substantially steadily and progressivelywhilst maintaining a relatively constant flow direction and achieving asubstantial portion of the flow area of the outer annulus prior to theouter annulus launch point and prior to the associated change indirection of the gas flow.

The mixer section may be characterized in achieving removal efficienciesof above 90% of particle sizes of less than 0.05 micron. The reactor maybe suitable for scrubbing waste gas from a modern high-performanceSinter Plant.

The mixer section may be provided with a scrubbing fluid inlet, thescrubbing fluid inlet being arranged to create relative adiabaticquenching of the gases. The adiabatic quenching of the gases may be to atemperature of between 20 and 60° C., and preferably to a temperature ofabout 30 to 50° C. The scrubbing fluid inlet may be arranged such thatthe bulk of the scrubbing fluid retains a large droplet form and a lowlaunch velocity relative to the droplet sizes and launch velocities inthe subsequent stages in the mixer section.

The equipment may include a cyclonic section for the separation of thegas and the scrubbing fluid, the cyclonic section preferably fittingwithin the same cylindrical profile as that of the mixer section.

In addition, the outlet for the scrubbing fluid is connected in an axialdirection and within the same overall cylindrical profile.

The gas and scrubbing fluid mixture typically exits in an axialdirection from either the inner or the outer diameter section of thevarying diameter annular profile of the mixer section. As a result ofthe position of the last launch point and the subsequent profile of theannular flow path, most of the scrubbing fluid will be on the outsidewall of the last bend as the mixture enters the cyclonic section, withonly splash and fine droplets remaining within the bulk gas flow.

The cyclonic section may be provided with an exit end in the form of avortex finder, configured and dimensioned to duct away the main vortexof substantially scrubbing fluid free gas while gathering thesubstantially gas free scrubbing fluid off the wall of the cyclonicsection.

The equipment may be provided with a relatively long cyclonic section inorder to retain the radial velocity component of the gas flow within thecyclone body within the range required to get the required degree ofseparation of scrubbing fluid droplets prior to discharging the gas.

The length of the cyclonic section preferably is characterised in thatthe distance between the spinner section and the top of the vortexfinder is about 5 to 10 times the diameter of the cyclonic section.

The cyclonic section may have a length of about 1.5 to 2.5 metres, andpreferably about 2 metres, and a diameter of about 0.1 to 0.5 metres,and preferably about 0.3 metres.

The equipment also may include a spinner section, having a set of angledblades for imparting a circulatory motion to the gas and scrubbing fluidmixture prior to entry of the cyclonic section. The width of the flowpath through the spinner section may be increased radially so that thecross sectional area for the flow is maintained relatively constant asthe flow direction changes, thus retaining relative exit velocities ofthe gas and the scrubbing fluid substantially similar to the respectiveentry velocities.

The spinner section may be configured and dimensioned so that any objectthat can pass through the main mixer section can also pass through thespinner section. The spinner section may be provided with an annulusthough which the gases and scrubbing fluid flow so as to calm the bulkof any residual turbulence from the spinner blades, and thereafterthrough a relatively simple cylindrical conduit. The annulus preferablyhas an inner, hollow profile with a deep cylindrical recess with aconical, alternatively, domed inner end in order to remove any dropletsof scrubbing fluid that contaminate the scrubbed and cycloned productgases.

The equipment further may include a discharge pipe centrally orientatedrelatively to the vortex finder, with a diameter of about 70 to 90% ofthat of the vortex finder outlet, providing an annular gap therebetween. The annular gap may be configured and dimensioned to pass anydebris that could access the equipment and wider than the typicalmaximum splash and spray layer that would accompany the scrubbing fluidas it runs down the inner walls of the cyclonic section. The gap ispreferably configured and dimensioned so that the minimum width of theannular gap at the vortex finder is based on the concept of capturingall such splash and spray into this annular area.

The equipment may be characterized in that the mixer section, thespinner section and the cyclonic section are cast in a single,substantially integral unit.

According to a second aspect of the invention there is provided a methodfor the removal of relatively fine particulates from a first substance,using a second substance, the method including the steps of transportingthe first substance and the second substance through a plurality ofstages in a flow path, at least some of the stages being shaped todefine a substantially curved flow path having an effective centre ofcurvature located to one side of the flow path, and wherein eachadjacent stage has a centre of curvature on an opposite side of the flowpath to provide a point of inflexion between adjacent stages with theflow path being provided with an edge formation between at least twoadjacent stages towards the point of inflexion and whereby, as the firstsubstance and the second substance flow through the reactor between theadjacent stages, particles present in the first substance migratethrough the second substance, first in one direction and then in asubstantially opposite direction to promote interphasic interactionbetween the first substance and the second substance; and launching thesecond substance on the outside of the curved flow path from the edgeformation at relatively high velocity to the inside of the curved flowpath of the adjacent stage.

The first substance may be a gas and the second substance may be ascrubbing fluid.

The method may be characterized in achieving removal efficiencies ofabove 90% of particle sizes of less than 0.05 micron. The method may besuitable for scrubbing waste gas from a modern high-performance SinterPlant, using a suitable scrubbing fluid.

The method may include the step of adding a relatively fine dustupstream of the mixer section to enhance the removal of vapours in thegas. The fine dust may be pre-selected so as to enhance thechemisorbtion on to the dust of gasses and vapours selected from thegroup consisting of dibenzo furan, PCB, related compounds and anycombinations thereof.

According to a third aspect of the invention there is provided aplastics material for the manufacture of the equipment for the removalof relatively fine particulates from a gas stream, the materialcomprising an abrasion resistant composite selected from the groupconsisting of a filler, Silicon Carbide and a vinyl ester resin.

The filler may consist of silica, alumina and/or glass fibre, and ispreferably subjected to Silane pre-treatment.

The Silicon Carbide may have a predetermined particle size and sizedistribution, and preferably consist of a combination of 10 and 60 meshparticulate material thus providing the required abrasion and impactresistance. Preferably, the Silicon Carbide consists of pre-selectedmixtures of 10 mesh solids with 60 mesh solids, thus obtaining thepredetermined mixing and flow properties that enhances the mouldingprocess and the ultimate abrasion and impact resistance of theequipment.

The material may include hollow or sponge-like fine particles so as toimpart a degree of elasticity and overall sponginess to the resin. Thefine particles preferably have sufficient chemical resistance so as notto degrade by the environment and are small relative to at least thelarger filler particles and, preferably are small relative to thesmaller filler particles. The fine particles may include hollow glassspheres and both hollow and sponge-like kaolin particles.

SPECIFIC EMBODIMENT OF THE INVENTION

A preferred embodiment of the invention win now be described by means ofa non-limiting example only and with reference to the various aspects ofthe invention and the accompanying drawings.

A single high intensity mixing and contacting device or so-called MSPR,was modified in accordance with the invention. The modified MSPR wasused in pilot plants designed for the removal of relatively fineparticulates from a gas stream, using a scrubbing fluid, and thesubsequent separation of the gas and the scrubbing fluid, the gas streambeing part of the hot off-gases from the Sinter and other furnacerelated processes at one of the Iscor Limited iron making facilities atVanderbilt Park, South Africa.

The hot off-gases from the Sinter and other furnace related processes,so-called sinter gas, was generated during the sintering of a mixture offine ores, additives, iron-bearing recycled materials from downstreamoperations such as coarse dust and sludge from blast-furnace gas (BFgas) cleaning, mill scale, casting scale and coke breeze. The modifiedMSRP is hereinafter referred to as an “IGCP unit”.

As a result of the gas to scrubbing fluid interaction in the IGCP unit,the gas temperature was reduced by a combination of simple heat transferfrom the cool scrubbing fluid and the latent heat of evaporation as someof the scrubbing fluid evaporated into the relatively low dew pointgases. At the same time, some of the component gases within the main gasstream dissolved into the scrubbing fluid and some also reacted withcomponents within the scrubbing fluid.

In the description, the IGCP unit itself is described, beginning at thegas and scrubbing fluid inlet into the IGCP unit and going all the waythrough the IGCP unit. After describing the details of all theindividual parts of the IGCP unit, the mounting arrangements for groupsof units are described together with all the relevant details of thecomponents within the main carrier vessel.

Following this, an overall application is described, indicating how thecarrier vessel and its contents form part of an overall process system.

The above descriptions are with reference to the accompanying drawings,wherein—

FIG. 1 is a diagrammatic layout of a 1% throughput pilot partincorporating an IGCP unit;

FIG. 2 is a diagrammatic layout of a 25% throughput pilot partincorporating a set of IGCP units;

FIG. 3 is a cross-sectional view of an IGCP unit, showing a centrallyarranged scrubber fluid feed;

FIGS. 3 a and 3 b depict the same cross-sectional view of the IGCP unit,showing the centrally arranged scrubber fluid feed on a larger scale;

FIG. 4 is a side elevation of an IGCP unit, depicting the same detailsas are shown in FIG. 3 a;

FIG. 5 is a profile of a stepped edge;

FIG. 6 is a detailed cross-section of an overall carrier vessel;

FIG. 7 is a cross-section of a typical scrubber fluid feed header forthe IGCP unit;

FIG. 8 is an exploded sectional view of a saddle and connection piecesfor the IGCP unit fluid feed;

FIG. 9 is a cross-section of a feed boss inlet arrangement with itssupport ring;

FIG. 10 is a plan view of a dust-cover to the IGCP unit;

FIG. 11 is a front view of a punch plate mounted support ring;

FIG. 12 is a cross-sectional view displaying components and equipment inarrangement within a carrier vessel;

FIG. 13 is a longitudinal section of a tail pipe and vortex finder area;

FIG. 14-15 are sectional views of the tail pipe and vortex finder area;

FIG. 16 is a detailed view of the body of the cyclonic section of theIGCP unit;

FIG. 17 depicts the support ring as a profile and in a front view;

FIG. 18 depicts a sectioned and a detailed plan view of a jigarrangement for manufacturing a punch plate;

FIG. 19 is a longitudinal front sectional view of a tie rod arrangementwith the core sections of the IGCP unit;

FIG. 20 is a partially sectioned front view of an attachment method forthe upper end of the tie rod to the scrubber fluid distribution targetpiece;

FIG. 21 depicts spinner blades in inner and outer profile;

FIG. 22 depicts plan and cross-sectional views of a pipe drainagesystem, incorporating the floor plate, support beams, plate support ringand pipe supports;

FIG. 23 depicts the two types of drains in partial cross-sectional view;

FIG. 24 is a front sectional view of the lower section of the a carriervessel also showing walkways, guide posts, gas outlet ducts and anadjacent carrier vessel with interconnecting walkway;

FIG. 25 depicts partial views of the carrier vessel in arrangement withthe main punch plate support;

FIG. 26 is an indicative process flow diagram of the gas cleaningprocess; and

FIGS. 27, 28, 29, 30, 31 and 32 are representative drawings of variousaspects of the equipment above, additional equipment and the equipmentfor the manufacture of the above equipment

1. THE BASIC FORM AND FUNCTION OF THE FLOW PROFILE OF THE MIXER SECTIONOF THE IGCP UNIT

1.1 The Form and Function of the Prior Art Flow Profile

The basic flow profile of the prior art MSPR consists typically of anannular passage that systematically changes diameter as a gas stream, orthe so-called main carrier gas, containing contaminants such as fineparticulates droplets, such as the hot off-gases from the Sinter andother furnace related processes, and a suitable scrubbing fluid, such aswater, progress along the passage. As a result, the gas is continuallychanging its radial velocity component from radially one way to radiallythe other.

In addition, the overall average speed of the gas is varied (i.e.increased and/or decreased) along the length of the annulus, e.g. at thechanges of direction, at the inner and/or outer radial positions (whenthe gas has essentially an axial velocity only) or progressively as itmoves through the overall profile.

Within this gas flow, the changing velocity components bring with themthe issue of the relative gas flow with respect to droplet and otherparticulates that are present The resultant relative velocities applyviscous drag from the gas to the droplets and particulates, which inturn changes their natural flow path within the gas flow and impartsrotational movements to the individual droplets and particles. Therelative and rotational movements between the gas and the droplets andparticulates promote intense interactive contact between all of thethree phases (solid, liquid and gas) with respect to each other.

In addition to these reasons for interactive contact, and as the mixturepasses around each corner in the flow profile, centrifugal forces areapplied to each of the three phases. The forces move any particles ordroplets that are less dense than the main carrier gas towards thecentre of the curvature and all particles or droplets that have a higherdensity than the main carrier gas are moved away from the centre of thecurvature. The relative movements of the particles and droplets thuscause further enhancement of the interactive contact between all of thethree phases with respect to each other.

1.2 Features of the Flow Profile in Accordance with the Invention

The flow profile of the mixer section of the IGCP according to thepresent invention is however shaped so as to collect and accumulatescrubbing fluid on the outside of each curve and to launch it at highvelocity from a sharp edge (or corner) at or near to the point ofinflexion (change of direction from concave to convex) between theoutside collecting surface and the start of the next inside curve.

Viscous drag on the surface of the profile causes the scrubbing fluid toleave the launch point at a velocity that is lower than that of theadjacent gas. This velocity difference not only causes the thin film ofscrubbing fluid to break up into small droplets but it also creates anintense interaction between the droplets and the gas and between thedroplets and any particulates or other droplets that are within the gas.

Immediately down stream of the launch point, the gas flow changesdirection such that all the gas has to pass through this finelydispersed and high velocity stream of scrubbing fluid droplets. Again,intense interaction occurs between the droplets and the gas and betweenthe droplets and any particulates or other droplets, which may be withinthe gas.

As a result of this intense interaction and as a result of generalviscous drag, the droplets of scrubbing fluid begin to take on a secondcomponent to their velocity, in line with this new gas flow direction.The finer scrubbing fluid droplets gain a higher velocity than thecoarser ones, because of their relatively smaller mass with respect tothe viscous drag, which is applied to them.

Soon after the change in direction of the gas flow, the gas flow changesdirection again and the finer droplets are subjected to a combination ofcentrifugal forces and simple inertia which cause them to move to theoutside of the gas flow passage. The shape of the gas flow passages issuch that the centrifugal forces are very high relative to normalgravity. As a result, the particles move towards the outside of the flowpassage at relatively high cross flow velocity, causing an interaction,the intensity of which is a function of gas velocity, droplet size andthe specific flow profile that is used.

1.3 The Resultant “Fight Path” of the Scrubbing Fluid in the FlowProfile

In the flow profile in accordance with the invention, the largerdroplets of scrubbing fluid first accelerate in the direction of gasflow and then substantially traverse the changed gas flow direction withrelatively little change in their direction of movement. This isachieved by the specifically arranged profile and by the launching ofthe scrubbing fluid from the point of inflection at the end of theprevious bend in the profile. Thus, the gas and what is suspended orotherwise present in the gas flow past the droplets as a high speedcross flow as the momentum of the droplets carry them across the flowprofile to collide with and mostly coalesce onto the opposite wall ofthe flow passage. As the gas continues on around the bend in the flowpassage, the smaller droplets arrive at the opposite side of the flowpassage by a combination of simple momentum resulting from their launchand centrifugal forces resulting from their acceleration in thedirection of the gas flow plus the ongoing curvature of the gas flowpassage. The finer droplets are less able to cross the gas flow passageas a result of their initial launch velocity, but because they will tendto attain a velocity which is closer to that of the gas, then, relativeto their mass they will be subject to much greater centrifugal forcesthan the medium and larger sized droplets. The centrifugal forces causethe majority of these fine droplets to move to the outside surface ofthe flow passage and for them to combine with the layer of scrubbingfluid, which has developed as a result of the larger droplets havingreached that surface.

A combination of the arrival velocity of each droplet and viscous dragfrom the gas as it flows around the bend causes the high velocity of thelayer of scrubbing fluid which accumulates on the outside of the flowprofile. As a result of the high gas velocity and general splash fromthe larger droplets, much of the layer will consist of a sequence ofdroplets being ripped off wavelets in the surface layer and beingaccelerated within the gas. A combination of centrifugal forces and theongoing curvature of the surface intersecting the flow path of thesedroplets causes the majority of these droplets to recombine with thesurface layer and, because of their increased velocity within the gasboundary layers, the layer of scrubbing fluid film gains speed. Theremainder of near the surface droplets inevitably stays close to thesurface layer.

At the next point of inflection a similar launch point is provided andthe process of re-launching a stream of droplets is repeated. Anydroplets of scrubbing fluid which leave the surface layer and do notrecombined with it before the surface layer passes this next launchpoint simply behave in a similar manner to the droplets which form fromthe surface layer as it leaves the launch point.

The re-launched stream of droplets interact with the particulates andother components of the gas stream, as well as collide with and capturefine droplets from the previous launch which were too fine to have madethe complete traverse of the flow passage. As a result, the net amountof scrubbing fluid which is launched from each successive launch pointis relatively constant at virtually the total scrubbing fluid flowsubstantially throughout the whole of the mixer section, other than fora potentially reduced flow at the second launch. In fact, the volume ofscrubbing fluid, which is launched at the second launch, is typicallygreater than about 80% of the total scrubbing fluid flow.

The net result of the various mechanisms influencing the “flight path”of all the different sizes of scrubbing fluid droplets from the launchpoint to the other side of the flow passage is that all the dropletstraverse the gap at high speed and, as the direction of their flight isbent in the direction of the gas flow, so the direction of the gas flowchanges some more. This ensures that the gas always endeavour tomaintain a generally perpendicularly orientated direction with respectto the velocity of the droplet. With the larger droplets, this relativedirection (once the droplets are clear of the launch point) is veryclose to perpendicular over the whole of the subsequent flight path.With the smaller droplets, this relative direction is not as close toperpendicular and the smaller the droplet, the further it is away fromperpendicular.

The further the respective velocity directions between gas and scrubbingfluid are away from perpendicular, the lower the resultant gas todroplet relative velocity. When the gas to scrubbing fluid velocity isreduced, so the number of dust particles, which are collected per unittime for a given size of droplet, also reduces. However, this is mostlycompensated for by the fact that the smaller droplets take longer tocross the gap. Therefore, the net scrubbing effect resulting from alonger exposure time to the gas stream per launch for small droplets,but with less intense exposure (or interaction) is similar to thatcreated for larger droplets where there is a shorter exposure time butwith more intense exposure.

1.4 The Benefit of Repeating Launches

A significant number of scrubbing fluid launch points arranged one afterthe other thus accumulates over successive launches into a very highremoval efficiency, what otherwise would only provide a relatively poorremoval efficiency for a given size of particle or fine droplet perlaunch of scrubbing fluid. Providing the gas velocity and all the flowprofiles and other criteria remain relatively similar over successivelaunches, the dust removal efficiency for a particular size of dust isrelatively constant for each successive launch.

Thus, for example, if say 30% of a specific size of dust is removed as aresult of one launch stage, then after 5 such launch stages, just over82% of that size of dust will be removed and after 10 such stages, alittle over 97% will be removed. Similarly and for example, at say 45%removal per launch, and after 5 launches, a total of about 95% will beremoved, while at 60% removal per launch, and after 5 launches, a totalof about 99% will be removed.

1.5 Scrubber Fluid Droplet Formation

The flow path of the present invention has a flow profile that is shapedsuch that effectively all of the scrubbing fluid leaves at the start ofeach inside curve and not at some point that is about 50% or more aroundthe curve.

Also, the scrubbing fluid leaves as a single flat layer (therebyensuring that no droplets are released within the shadow of dropletswhich left a little earlier). Furthermore, effectively all of thisscrubbing fluid reaches the far side of the flow profile before thefluid on that side is released at the commencement of the next bend. Inaddition, the introduction of axially (or near axially orientated)straight sections to the flow profiles ensures that

-   -   a) when the fluid reaches the far wall it arrives at an angle of        approach which is as close as possible to zero, such that as        much as possible of the energy of the droplets is recovered        within the surface film (which also minimises abrasion); and    -   b) the distance from the “landing zone” for these droplets to        the re-launch point is as short as possible so as to minimise        the subsequent effects of viscous drag on this “landing        velocity”.

Effectively, complete launching of the fluid is achieved by creating thestep at the start of each inside radius. The angle of the lead up tothat step sets the launch angle of the droplets. It is envisaged thatthe launch angle can be set to suit the shape, proximity and width ofthe subsequent bend. In this way, maximum contact between the launcheddroplets and the gas is achieved, each time they are launched.

Typically, there is always a minor “dribble” of scrubbing fluid aroundthe edge of a stepped edge, especially when the edge is not sharp, e.g.as a result of wear or other forms of damage. If such a “dribble” is ofsufficient magnitude that further on around the inside of the bend, the“dribbled” fluid would form a significant “drip off” zone, this fluidwill not create that much of a scrubbing function per unit of scrubbingfluid that is released. However it will still absorb almost as muchenergy per unit of scrubbing fluid as that which is launched from thestepped edge.

In order to avoid this loss of efficiency, the detail of the steppededge has been developed to have a subsequent ledge just beneath thestep. This ledge is arranged so as to encourage a small back eddy of gasimmediately beneath the main step which will sweep any downwards flow of“dribble” back up again into the underside of the main fluid flow as itleaves the main step. In this way, the fluid that would have been in the“dribble” is put back into the main flow of scrubbing fluid, therebyensuring maximum scrubbing effect for effectively the same energy usagethat would have occurred had the “dribble” been allowed to flow clear ofthe step to a subsequent “drip off” zone part way around the curve.

2. Preferred Orientation for the IGCP Unit

The normal and preferred arrangement for an individual IGCP unit is withits axis vertical with the input gas and the clean scrubbing fluidinlets at the top. In the preferred arrangement, the scrubbed gas andthe used scrubbing fluid exit separately from the bottom of the unit inseparate ducts. Although the unit performs relatively efficiently in ahorizontal orientation, the ultimate performance is affected by gravity,which causes an initially uniform distribution of scrubbing fluid withinthe gas flow to become sufficiently non-uniform to affect the scrubbingperformance. This effect from gravity is largely overcome by using aslightly higher flow rate of scrubbing fluid, however, this does createan overall higher gas pressure drop within the unit for the same degreeof performance.

3. Various Features of the Mixer Section of the IGCP Unit

3.1 Scrubbing Fluid Inlet into the IGCP Unit

The scrubbing fluid can be fed into the inlet of the unit in a number ofways. The choice depends upon the nature of the dust, which is to beremoved. When dust is not present, i.e. for simple contacting of gaswith scrubbing fluid, the choice of scrubbing fluid inlet should bebased on simple economics and practicality.

For process reliability and cost reasons, the use of spray nozzles isavoided. If the dust (or part of the dust) has the potential forreacting with the scrubbing fluid to form a concretion which hardenswith time, then it is essential to prevent any of the dust from beingable to settle or accumulate onto a wet surface or onto a surface wherecapillary action or occasional splash could sufficiently wet the dust soas to cause the concretion process to proceed.

In this invention, four different techniques for feeding the scrubbingfluid have been envisaged that will overcome the problem of concretion.

The four concretion resistant options are:

-   -   a) An arrangement with a single central feed which is directed        to a shaped central target piece which breaks the flow into a        uniformly spread radial flow. This radial flow is usually        horizontal or slightly down from horizontal. However, it may be        angled slightly upwards or further downwards from horizontal.        The inlet gas flows around the centre feed and is also spread        radially outwards by this target piece. Before the gas reaches        the outer wall of the cylindrical IGCP unit, the circular entry        cowl (or ring) causes the direction of gas flow to change from        partially radial to axial and then the gas enters the annular        flow profile of the IGCP unit Before the gas enters the IGCP        unit flow profile, it flows through the radial flow of scrubbing        fluid.    -   The scrubbing fluid naturally wets and irrigates the inner        surface of the annular flow profile of the IGCP unit and once it        has traversed the annular gap, it wets the outer surface as        well. The shape of the central target is such that not only is        the inlet velocity of the fluid maintained (so as to give the        fluid sufficient momentum to carry the majority of itself across        the gap) but also the incoming gas has to accelerate across the        top of the radial flow of scrubbing fluid over the surface of        the target piece, in order to gain the necessary speed to enter        and pass through the annular flow profile of the IGCP unit. The        consequent high velocity gas flow causes the scrubbing fluid to        be accelerated as a result of viscous drag from the high        velocity gas, firstly in a radially outwards direction whilst it        is still flowing on the surface of the target piece and then in        a downwards or axial direction as the gas turns to flow down (or        along if the IGCP unit is arranged horizontally) the annular        flow profile.    -   As a result of this arrangement, the scrubbing fluid first        strikes the wall of the IGCP unit below (or downstream) of the        circular entry cowl. In addition, the shape of the wall at this        point is such that the fluid strikes the wall at a relatively        shallow (or glancing) angle and as a result all potential        splashes are in the general direction of the gas flow, even if        those splashes have a significant radial component. There is        therefore an almost single line contact between the fluid and        the outer wall of the annulus, i.e. a single line between dry        wall and wet wall. Any dust which settles onto the wall at this        line will be in a high velocity and hence high shear area. As a        result, dust accumulation is unlikely to occur and if it does,        it will only accumulate very slowly.    -   With this type of entry and when there is the potential for        concretion, it would be normal for the IGCP unit to be arranged        with more than one unit. Typically they would be arranged into a        minimum of four groups. On a sequential basis one group would        have its gas input stopped while the other three (or more)        groups would share the extra load. The scrubbing fluid would        remain on. The shape of the central target piece, its position        relative to the circular entry cowl and the shape of the        downstream side of this cowl are such that when the gas flow        stops, the fluid will strike the wall a little further upstream        and at a more acute angle. The more acute angle will both reduce        splashing and assist the rapid wash off of any commencement to a        concretion build up.    -   After what should normally be a few seconds, the gas flow can be        restored to that group of units and each in turn of the other        groups of units can be similarly washed clear of any concretion.    -   The frequency of these wash offs will be determined by the rate        of the chemical concretion reaction. Typically, wash off should        not be necessary more than once every few hours, even in the        presence of high dust loads with very rapid chemical reactions.    -   This style of concretion prevention lends itself to situations        where the inlet gas is hot and where the wet surface created by        the washing off process will dry rapidly because of the heating        effect from the thermal mass of the circular entry cowl and the        drying effect of the high velocity hot gases flowing past the        surface.    -   In many circumstances, this same wash off procedure can be        achieved by simply reducing the gas flow (rather than stopping        it) on that group of units for a few seconds.    -   Alternatively the wash off can be achieved by increasing the        scrubbing flow to that group of units. An increased scrubbing        fluid flow will cause the fluid entry velocity to increase        thereby increasing the radial component of the velocity of the        fluid as the fluid flows across the surface of the target piece        and then on across the annular gap to the outer wall of the IGCP        unit. This increase in velocity and overall momentum (resulting        from both increased mass flow and velocity) will cause the fluid        to strike the wall slightly upstream of the normal position,        thereby achieving the necessary wash off of any concretion.    -   Usually, increasing the scrubbing fluid flow rate increases the        gas phase pressure drop across the unit. Therefore, an increase        in the scrubbing fluid flow rate to a group of units will        normally cause some of the gas flow to re-direct itself        automatically to the other units. The resultant reduced gas flow        to the units which are being washed will therefore assist the        process.    -   It should be remembered, however, that with particularly        reactive dusts, gas flow stopping may be necessary for each wash        off, or after a small number of washes from one of the above        styles of “flow adjustment” washes.    -   If the inlet gas temperature is at, near or below its dew point        then this design option may not be appropriate. However, for all        other circumstances it would normally be the preferred design        because of its constructional simplicity and because of its        ability to handle low scrubbing fluid volumes with minimal        potential for blockage or mal-distribution.    -   b) An arrangement which functions in a very similar manner to        that of the previous design but which uses a standard hollow        cone spray nozzle with a wide spray angle to create the initial        radial flow of scrubbing fluid. Preferably, the nozzle should        have a relatively low feed pressure and should use a tangential        inlet feature to create the hollow cone spray, as these styles        tend to produce less occasional droplets outside the main cone.        This system has the advantage that it is possible to change the        cone spray angle slightly by varying the scrubbing fluid feed        pressure, thereby avoiding the need for frequent gas flow        adjustment or stoppages in order to effect the wash off of any        concretions.    -   However, most styles of hollow cone nozzle will produce        occasional droplets which are outside the normal spray pattern        and the outlet of the nozzle is normally subject to concretion        build up which can have a pronounced effect upon the uniformity        and shape of the spray pattern. Once the spray pattern becomes        distorted, then concretion problems around the circular inlet        cowl will be more likely.    -   Despite this potential draw back, this inlet style for the        scrubbing fluid has many advantages, especially when it is        difficult for the gas feed to be stopped on individual or groups        of IGCP units, or when concretion is not too severe.    -   c) An arrangement with a single or multiple tangential feed        arrangement which feeds tangentially into an annular flow        channel which is located just upstream of the entry to the        annular flow profile of the IGCP unit. This style of scrubbing        fluid inlet is only really suitable for IGCP units that are        arranged with a vertical or near vertical axis.    -   The tangential feed(s) should enter the annular flow channel        from either the top (or the bottom) near the perimeter of the        flow channel or from the perimeter of the flow channel in such a        way as to minimise the potential for splashing. The flow channel        should have a horizontal or near horizontal floor (i.e. within        the range of about + or −30° relative to the horizontal) and        this floor should continue radially inwards from the channel.        Once it is clear of the annular channel this floor should        preferably slope downwards. This slope should be preferably in        the range of 20 to 70° from the horizontal, but angles greater        or lesser than this range can be used, depending upon the nature        of the scrubbing fluid, the volumetric flow of scrubbing fluid        relative to the gas flow and the size of the IGCP unit.    -   Gas would enter the IGCP unit from above this conically sloping        surface, accelerating as it moves down the cone. At a point        where the gas velocity has risen to a high enough level        (typically to around 0.3 to 1.3 times the average velocity        within the annular profile of the IGCP unit) then the conical        surface should change abruptly to a co-axial (or near co-axial)        cylindrical hole which should direct the combined flow of gas        and scrubbing fluid down onto the top of the core of the IGCP        unit. This top should preferably be co-axial or near co-axial        with respect to the cylindrical hole and it should have a domed        top, or should be finished with a torrispherical or some other        form of rounded conical or otherwise pointed end. This end        should have a uniformly symmetrical profile with respect to any        orientation about the axis of the IGCP unit, so as to shed all        the scrubbing fluid which lands on this top end of the core of        the IGCP unit, uniformly around its perimeter.    -   The top of the core should be positioned low enough with respect        to the conical section such that at least some of the fluid        flowing down the conical section will routinely cross the centre        line of the cylindrical section before it reaches the top of the        core. Additionally, or alternatively, especially where the        conical section has a relatively steep slope, the slope of the        last part of the conical section just before the cylindrical        section can be reduced so as to impart a greater radial        component to the velocity of the scrubbing fluid as it leaves        the end of the conical section. In this way the fluid will not        only wet uniformly the walls of the cylindrical part of the        entry but will also wet the top of the core and as a result it        will uniformly distribute the scrubbing fluid over the walls of        the core below it.    -   The essential part of this design is the design of the dust        shrouding over the tangential inlet and the annular flow channel        especially at the water exit from that channel on to the surface        of the conical section. Any splashing which occurs within the        annular flow channel must be contained by this shrouding and        must be returned to the annular flow of scrubbing fluid,        together with any condensation that may occur within that area.    -   The method of return is also critical. As the scrubbing fluid        emerges from beneath the dust shrouding, the edge of the        shrouding should be arranged so that the incoming gas flow        carries all the dust with it as it proceeds down the cone and        into the IGCP unit. Turbulent back eddies at the edge of the        shroud have to be minimised. Also, this lower edge of the shroud        must remain dry at all times. The design which has been        developed achieves as smooth a profile as is practical for the        gas flow (with minimal potential for back eddies) and has a        system for the collection of all splash and condensate and a        dedicated drip edge to keep all such scrubbing fluid clear of        the inner diameter and lower edge of the dust shrouding.    -   The design also includes for the leading face (gas side) of the        shroud to be a separate piece relative to the splash and        condensate cover for the annular flow channel. Whilst this makes        the shroud more complex, it creates an insulating gas filled gap        between the incoming gas and the wall of the annular flow        channel. This reduces the heat transfer between the incoming gas        and the scrubbing fluid and thereby reduces condensation if the        gas is cooler than the scrubbing fluid and also (when the gases        are hotter than the scrubbing fluid) it reduces evaporation and        crystallisation of any splash derived droplets that may stick to        the upper surfaces of the flow channel. This will prevent the        build up of any resultant crystals that could affect the        performance of this annular flow channel.    -   By having this outer piece separate, then it is possible to lift        it clear and remove any concretions that may have built up under        the inner drip edge whilst the system is working. This easy        access significantly simplifies and speeds up any necessary        maintenance.    -   The above described tangential feed arrangement probably        represents the ultimate in long term avoidance of concretion        problems, especially when gas shut off as in a) above is not an        appropriate option. However, it is not possible to reduce the        scrubbing fluid flow to such a low level as can be achieved with        option a) or b) whilst at the same time maintaining a        sufficiently robust total wetting of the inlet conical section        to enable it to always rinse off any concretions that can occur        during a process upset or as a result of an agglomerate of dust        (which, for example, could have fallen off ductwork, or        wherever, upstream of the unit) landing on the surface of the        conical section. In addition, in order to minimise back eddies        in the gas flow at the inner and lower edge of the shroud, the        gap through which the scrubbing fluid must flow must be kept as        small as possible. This in turn requires good upstream debris        removal to be arranged within the scrubbing fluid feed.    -   d) The fourth arrangement is basically a combination of        options a) and c). This option is more compact (as the top of        the core can be much higher up in relation to the position of        the tangential inlet) and it lends itself to situations where        larger diameter IGCP units are being used.    -   This option has similar reliability to that of option c) and        does not need to have regular gas or scrubbing fluid flow        alternations or gas stoppages in order to enable it to keep        itself clear of concretions.    -   However, higher scrubbing fluid flows are needed per unit of gas        volume flow, because of the two feed systems.

It was found that where the problem of concretion is not expected tooccur, options a) and b) are the preferred choice of scrubber fluidinlet

3.2 Scrubber Fluid Droplet Rotation

In addition to the droplet forming effect of the intense interactionresulting from the velocity difference between the gas and the film ofscrubbing fluid that exists immediately down stream of the launch point,the design of the launch point introduces a second rotational effect.The shear forces within the film of scrubbing fluid just upstream of thelaunch point cause the outer surface of the scrubbing fluid to be movingmuch more quickly than the inner surface. As a result, when thescrubbing fluid film leaves the solid surface at the launch point(stepped edge) the different velocities of the inner and outer surfacesof the film not only assist the break up of the film into droplets, butalso cause the resultant droplets to have a high rotational velocity.

The rotation of the droplets results in the following:

-   -   a) Large droplets immediately break up into smaller droplets,        increasing the surface area of scrubbing fluid droplets for a        given volume flow of scrubbing fluid;    -   b) The smaller droplets tend to create a relatively closely        sized dispersion of droplets;    -   c) The boundary layer around each droplet is markedly changed        from that which would be normally expected. The shape of the        boundary layer, the position of the break away of the peripheral        vortices and the orientation of the final wake are all changed        significantly as a result of the droplet rotation relative to        those that would be associated with the simple trajectory of a        hardly rotating droplet through a gas flow.    -   d) In addition, the plane of rotation for each droplet is        parallel to the local flow profile of the gas.

It is clear that items a) and b) above will significantly enhance theinteraction between the scrubbing fluid and the gas, and between thescrubbing fluid and the particulates or other droplets in the gas. It isalso clear that as a result of the relatively small and closely sizedscrubbing fluid droplets there will be a considerably larger number ofdroplets relative to the number that would be formed by the “drip off”mechanism referred to above. Also, the close size range will ensure thatthe shape of the flow profiles can be arranged to achieve optimum“flight” of these droplets through the gas, following each launch.Further, the shape of the flow profiles can be arranged to achieveoptimum recombination (or landing) of the droplets onto the outersurface of the flow profile ready to create the next layer of scrubbingfluid, ahead of the next launch.

The benefit of c) and d) is somewhat more technical and becomes morerelevant as the particle size of the dust (or fine droplets) which areto be removed from the gas stream get smaller. The benefit of c) and d)also becomes increasingly relevant when simple gas to liquid (or liquidor dissolved component to gas) diffusional type processes need to beintensified. The boundary layer changes that will create thisimprovement to diffusional type processes will become clear as the dust(or fine droplet) situation is explained.

3.3 Uniformity of Gas Velocity

As a result of the pressure drop over the IGCP unit the pressure of theoutlet gas is lower than that of the inlet gas. The actual volume flowof gas at the outlet is therefore greater than at the inlet (assumingthere is no significant temperature change or gas absorption/desorptionover the length of the unit).

With this type of equipment, in order to achieve optimum energyconsumption for a given degree of dust or mist removal for a particulardust or mist particle size, it can be shown that the basic relationshipsbetween gas velocity, droplet size and droplet velocity need to remainessentially constant over the length of the unit. The flow profile,therefore, has to be adapted progressively throughout the length of theunit in order to achieve this. This maintenance of the essentialvelocity profiles has the added bonus that abrasion, which wouldnormally be much more severe at the outlet end of the unit than at thebeginning, can be made to be essentially uniform over the whole of theunit. This has a marked benefit on the operational on-line time betweennecessary maintenance. In this regard, it should be noted that the typeof wear which will result on the profile surfaces of the IGCP unit willbe mostly derived from droplet impingement and general slurry velocityin the surface films of scrubbing fluid. This sort of wear is typicallya function of slurry impingement velocity and of surface velocity, eachraised to a power x and y respectively where x and y have values ofbetween about 3 and 5, depending upon the specific circumstances.

In a typical situation where the actual exit volume flow of gas from theIGCP unit is about 15% more than the inlet volume flow, wear at theoutlet end could be in the region of almost twice that at the inlet.Therefore, by arranging the gas velocity to remain as constant aspossible throughout the IGCP unit, not only is energy being saved for agiven degree of dust removal, but also the equipment life betweenessential maintenance is almost doubled.

3.4 Maintenance of the Scrubber Fluid Droplet to Gas Relative Velocityin the Inner Annulus

Ii is envisaged that for the actual gas velocity to remain constant inboth the inner annulus and the outer annulus, the width of the innerannulus must be significantly greater than that for the outer annulus.This will require that the “flight path” for the droplets to besubstantially longer within the inner annulus than within the outerannulus. Simple viscous drag however will ensure that the relativevelocities between the scrubbing fluid and the gas will be substantiallylower at the end of its flight path relative to those at the beginning.

As the relative velocities decline, so the ability of the scrubbingfluid droplets to remove fine dust and other particulates declines muchmore rapidly. A combination of different launch angles and different gasvelocities down the inner and outer parts of the flow profile aretherefore required to maintain the dust/particulates removal efficientlyper scrubbing fluid launch, while the resultant increase in wear andenergy consumption need to be minimised.

An increased launch angle of between about 3° and 10° relative to thatwhich is used for the outer annulus together with an increased gasvelocity down the inner annulus of between about 5 and 25% relative tothat down the outer annulus has been found to be effective in restoringthe dust and mist removal efficiency per launch of the inner annulus tothat of the outer annulus. It is envisaged that the finer the dust ormist particle that is to be removed, the greater the difference that isneeded for optimal removal efficiency.

It is envisaged that the although the gas velocity down the innerannulus could require raising, the bend that gathers the scrubbing fluidready for launching into the outer annulus could be configured anddimensioned such that the scrubbing fluid droplet impingement and filmvelocity on this bend and at the subsequent launch point are no moresevere than for that at the equivalent point in the outer annulus.

It is further envisaged that suitable configuration and dimensioning ofthe flow profile leading from each inner annular zone to the respectivefollowing outer annular zone could optimise recovery of the extravelocity energy in the inner annulus area back to pressure energy at theouter annulus, such as by shaping the profile downstream of the landingzone for most of the droplets so that the flow area increases steadilyand progressively whilst maintaining a relatively constant flowdirection and achieving the full flow area of the outer annulus prior tothe outer annulus launch point and prior to the associated change indirection of the gas flow.

In FIGS. 3, 3 a, 4 and 32, the profile, which is shown, is of the typethat maintains a constant gas velocity throughout the flow profile.FIGS. 27, 28 and 29 show a profile that has been adapted to create amore uniform dust removal efficiency per launch whilst maintainingrelatively uniform wear throughout the unit

3.5 Other Uses for the Feed Boss Support Spokes

As drawn in FIG. 9, the feed boss support spokes (101 in FIG. 9) havetheir major axis in line with the gas flow into the IGCP unit. A furtherfeature of the development is to improve the functionality of the unit,especially as regards the quenching of hot inlet gases and assisting theuniformity of scrubber fluid distribution around the whole perimeter ofthe annulus, is to angle these spokes so as to impart a circulatory spinto the gas as it enters. Preferably, for energy conservation reasons,the gases should be spun in the same direction as the spinner sectionwill direct them. However, spin in either direction will enable theimprovements to the quench and to scrubber fluid distribution to beachieved.

4. Separation of the Gas from the Scrubbing Fluid

4.1 General Overview

In general, the gas and scrubbing fluid will be flowing along an annularflow path as they exit the contacting profile. It is envisaged thatwhilst the prior art MSPR are typically applied to almost anyarrangement for the contacting profile, the generally convenient andeasy to construct and operate form typically would utilise an annularform.

In the present invention, the separation of the scrubbing fluid from thescrubbed gas is carried out with a cyclonic section. It is envisagedthat the cyclonic section, could be followed, if necessary, by some formof further mist elimination. The scrubbing fluid is recycled (followingchemical treatment, as necessary, and the removal of suspended solids.

The cyclonic section fits within the same cylindrical profile as theannular body of the mixer section. This cyclonic section is arranged toenable the maximum gas flow and scrubbing fluid flow that can beaccommodated within the mixer section to be separated with highefficiency. In addition, the outlet for the scrubbing fluid is connectedin an axial direction and also within the same overall cylindricalprofile.

As a result of all these components being within the same overallcylindrical profile, then multiple units can be arranged side by side ina very compact array, so as to be able to handle whatever gas flow thatis required using the appropriate number of standard IGCP units.

For a given degree of removal of a particular size of dust or finedroplets, there is an optimum width of flow profile and hence areasonably optimal diameter for the overall annular profile. For highremoval efficiencies of very small particles, the annular gap has to berelatively small, e.g. no more than about 30 to 50 mm for >90% removalof 0.03 micron dust. Larger particles can be removed using similar orlarger gaps. Smaller particles are best removed using smaller gaps.

4.2 Typical Details of the Cyclonic Section

The gas and scrubbing fluid mixture typically exits in an axialdirection from either the inner or the outer diameter section of thevarying diameter annular profile of the mixer section. As a result ofthe position of the last launch point and the subsequent profile of theannular flow path, most of the scrubbing fluid will be on the outsidewall of the last bend as the mixture enters the cyclonic section, withonly splash and fine droplets remaining within the bulk gas flow.

Initially, this annular flow is put through a spinner section, having aset of angled blades, so as to impart a circulatory motion to themixture. The width of the annulus in the spinner section is increasedradially, so that the cross sectional area for the flow is maintainedrelatively constant as the flow direction changes, thus retaining exitvelocities substantially similar to the entry velocities.

It is envisaged that higher or lower exit velocities from the spinnersection could be obtained with specific blade design. More particularly,it is envisaged that a reduced velocity would enable good velocityrecovery and hence pressure recovery but with reduced removal efficiencyof any fine droplets of scrubbing fluid within the subsequent cyclonicsection. Similarly, it is envisaged that higher exit velocities wouldresult in better removal efficiency of the fine droplets of scrubbingfluid but with relatively higher overall pressure drop and wear rate onthe walls of the cyclonic section and the spinner section.

In this preferred embodiment, the spinner section exit velocities aregenerally of the same order of magnitude as the entry velocity into thespinner section.

In order to minimise the potential for blockages as a result of debris,etc, the spinner section is configured and dimensioned so that anyobject that can pass through the main mixer section can also passthrough the spinner section. It is envisaged that although largernumbers of smaller blades generally provide a more efficient and morecompact arrangement, the efficiency can be retained with a smallernumber of blades, by fitting a suitably designed trailing edge to eachblade which overlaps that of the next blade so as to create asubstantially parallel sided exit slot for the gases.

The gases and scrubbing fluid flow from the spinner section through ashort annular portion where the bulk of any residual turbulence from thespinner blades is calmed, and thereafter through a relatively simplecylindrical pipe portion. Typically, the end of the inner profile ofthis annular portion accumulates droplets of scrubbing fluid that tendto drip off and join the central vortex of scrubbed gases. These gasesin the vortex would be effectively free of scrubbing fluid droplets,other than for those that could drip off the end of this surface.

With no effective means within the core of the vortex of causing thedripped off droplets to be accelerated radially out of the core, thedroplets contaminate the scrubbed and cycloned product gases. In orderto prevent contamination, the inner profile of the annulus is hollowwith a deep cylindrical recess and with either a conical or a domedinner end to the hollow recess in order to remove any droplets ofscrubbing fluid from that portion of the gas which inevitably movesaround the stationary surface at the top of the cyclonic section to jointhe small central vortex which will form down the centre of thiscyclonic section. In effect, this small volume of gas is forced to flowthrough its own mini cyclone as it travels towards the central core. Thecollected scrubbing fluid from this mini cyclone is then arranged toflow back, normally by gravity, to the end of the annular portion belowthe spinner section and to join the main flow of gas down the maincylindrical body of the cyclonic section.

At the exit end of the cyclonic section, there is a vortex finder thatducts away the main spinning core (or vortex) of gas that is now free offine droplets of scrubbing fluid. The vortex finder also gathers thescrubbing fluid, off the wall of the cyclonic section, into anessentially gas free fluid and pipes it out of the bottom of thesection.

In order to achieve this, the clean gas is passed into a centrallyorientated pipe, which will typically have a diameter of about 70 to 90%of that of the cyclonic section. The larger the diameter of the cyclonicsection, the larger this percentage can be. The annular gap between thecentrally orientated pipe and the cyclonic section comparison is wideenough to pass any debris that could access the unit and wider than thetypical maximum splash or spray layer that would accompany the scrubbingfluid as it runs down the walls of the cyclonic section.

It must be noted that typical industrial cyclonic separators operatewith maximum tangential velocities of around 20 to 25 metres per secondwith some designs of wet systems getting up to around 30 to 35 metresper second. This limit enables. In this design, due to relatively highmaximum tangential velocities of around 20 to 35 metres per second,reducing the ease with which the droplets and the particulates are to becollected and flow reasonably smoothly down the walls of the cyclonicsection without excessive re-entrainment as a result of splashing,bouncing etc, the minimum width of the annular gap at the vortex finderis based on the concept of capturing all such bounce and splash intothis annular area.

At the bottom of the annular gap there are two part ring pieces eachcovering about 140° of rotation with a gap of about 40° of rotationbetween each ring. The function of these ring pieces is to provide aperpendicular end to the annular passage outside the clean gas outletwhilst enabling sufficient flow area through this end for the scrubbingfluid, together with some entrained gas, to enter the space beyond therings and for this entrained gas to pass back out again into the annulusonce it has been mostly separated from the scrubbing fluid.

The annulus extends beyond the two ring pieces where radial baffleswithin the annulus stop the rotation of the gas and scrubbing fluid andallow the liquid to fall by gravity towards the scrubbing fluid outletand for the gas to disengage itself from the scrubbing fluid and to befree to flow back out through the gaps between the ring pieces. Becauseof centrifugal force, the scrubbing fluid will flow through the gapspredominantly in the area towards the outer radius of the annulus andthe disengaged gas will flow back out of the gaps in the area towardsthe inner radius of the annulus.

As this disengaged gas is displaced back up the annulus it will gatherrotational speed as a result of viscous drag from the scrubbing fluidand entrained gas rotating in the outer part of the annulus. As thedisengaged gas increases in rotational speed, any fine droplets ofscrubbing fluid contained within it will be spun to the outside andreturned to below the two ring pieces. The length of the annular gapbetween the rings and the clean gas outlet is determined by the need tospin all such fine droplets of scrubbing fluid out of this return flowof gas before the gas reaches the clean gas outlet. Typically, thenecessary length of this annulus is within the range of 60 to 100% ofthe diameter of the cyclonic section.

Normally, the clean gas outlet is conveniently curved slightly (usuallyradially) to one side so as to make more room in the baffled area beyondthe two ring pieces for the piped outlet for the scrubbing fluid to beconnected, without unduly restricting the size of this outlet.

Whilst the above text refers to two rings, the ideal design from thepoint of view of the separation of the scrubbing fluid would use morethan two rings and appropriately smaller gaps. However, except for thelarger potential sizes, the practical issues of blockage prevention andeconomics of construction relative to complexity and ideality pointtowards two rings. Typically, for a two-ring arrangement, the rings needto occupy about 100° to 160° out of the 180° with the remainder beingopen. When the ring exceeds 160°, there is not normally enough space fordebris and for gas and scrubbing fluid interchange. When the ring coversless than 100°, too much turbulence tends to get past the rings into thebaffled part of the annulus and, as a result the separation performanceof the vortex finder as a whole is impaired.

Where the clean gas outlet is bent away from the overall centre line inorder to facilitate a larger outlet connection for the scrubber fluid(within the same overall cylindrical profile), it is necessary toutilise two rings and an extension to the baffling so as to prevent thechanging annulus beyond the rings from causing too variable a flow ofgas back out of the gap between the rings. The use of two ring piecesrepresents a good compromise in this instance, otherwise one ringsection could be suitable for the smaller diameter cyclonic sections.

In the preferred embodiment, the gas outlet is arranged through a slopedside plate and uses the side plate as means of closing off the annulusbeyond the rings and of supporting the outlet pipe for the scrubbingfluid, whilst at the same time forming part of the necessary baffling.

In view of the high gas inlet velocities relative to those typicallyfound within industrial cyclone separators, a relatively long cyclonicsection is used in order to keep the radial velocity component of thegas flow within the cyclone body low enough to get the degree ofseparation of scrubbing fluid droplets that is normally required beforethe gases is safely discharged to atmosphere, alternatively, to the nextprocess stage within the overall production process. The optimum lengthbetween the spinner section and the top of the “vortex finder” section(the top of the clean gas outlet) was found to be between 5 and 10 timesthe diameter of the cyclonic section. At lengths below 5 times thediameter, too many fine droplets remain in the clean gas and furthermist elimination is needed, while at lengths in excess of 10 times thediameter, the rotational velocity is so reduced as a result of the wallfriction that there is a rapidly declining economic benefit associatedwith further length increases. It is envisaged that if a greater degreeof removal of scrubbing fluid is required, it would be more beneficialto add a second spinner section and cyclonic section or to add a furtherIGCP unit.

With a cyclonic section with a length of about 2 metres and a diameterof about 0.3 metres together with appropriately designed spinner sectionblades, the removal efficiency of a clean water scrubbing fluid exceeded98% removal of 20 micron droplets.

5. Other Specific Features and Their Application

5.1 General Equipment Manufacturing Details

The following features and other general assembly details have beendeveloped or optimised as part of the IGCP unit and its associatedprocess equipment.

The IGCP unit consists of an arrangement that is easy to cast and easyto assemble, and which do not require specialist tooling, jigs or otherhigh quality technology or quality control arrangements in order toassemble them. The shapes of the components are such as to enable themto be cast of mixtures of suitably corrosion, abrasion and temperatureresistant resins, plastics and elastomeric compounds with suitablyabrasion resistant and thermally stabilising fillers.

In particular, the spinner section is such as to enable the casting ofsubstantially the entire IGCP unit as a single integral unit.

The scrubbing fluid inlet arrangements have also been arranged to becreated from standard as cast or as machined components which are jigmounted and resin bonded into standard constructions and which canenable the most corrosive of environments to be accommodated withrelative ease.

5.1.1 Scrubbing of Sinter Process Off-Gases

The off-gases from the Sinter Process have a temperature of around 150°C., with a short duration maximum of around 180° C. to 200° C. The gasescontain the products of a carbon fuelled combustion process with arelatively large amount of excess air. The gases also contain dust,products of incomplete combustion (including dibenzo-furans, PCB's andrelated compounds), acid gases (derived from sulphur and otherimpurities in the feed stocks) and condensed fumes. These fumes containcondensed alkali and other metal salts (usually chlorides) and condensedsilica compounds with other similarly sized fine particulates resultingfrom decrepitation and other processes that occur within the sinteringprocess.

It is envisaged that careful control of the pH of the scrubbing fluidwould enable the precise control of the removal of the acid gases. Thisprecise control results from the relatively high mass transferperformance of the IGCP unit relative to that typically achieved withintypical wet electrostatic precipitator (“WESP”) systems.

In addition, the whole IGCP unit based system is constructed in suitablyreinforced plastics and resins. This avoids all the pH, wet metaltemperature and high chloride limitations that are implicit with thenecessary metallic components within WESP's, as well as enables thescrubbing fluid to be maintained at a relatively acidic condition. Bykeeping the scrubbing fluid acidic, acidic gases can be removedselectively in accordance with specific environmental compliance (withconsequent savings in reagent consumption and residue disposal volumes).Also, the issues associated with concretion are much more easilycontrolled when the pH is kept low.

5.1.2 The Removal of PCB and Related Compounds from Sinter ProcessOff-Gases

The dibenzo furan, PCB and other related compounds typically chemisorbon to the fine particulates that are present in the Sinter off-gasses.This chemisorption process is favoured by low temperature and maximumcontact efficiency between the fine particles and the gases before thefine particles are wetted with the scrubbing fluid. The design of thescrubbing fluid inlet arrangements to each IGCP unit and the dustremoval efficiency of the first stage of the IGCP unit have been adaptedso as to exploit this situation.

The scrubbing fluid inlet is arranged to create good so-called adiabaticquenching of the gases, to a temperature, which is typically within therange of 30 to 50° C. This temperature depends upon the moisture contentand temperature of the off-gases leaving the combustion process. Also,the scrubbing fluid inlet is arranged such that much of the scrubbingfluid remains in a relatively large droplet form and has a relativelylow launch velocity with respect to the droplet sizes and launchvelocities that will apply to the successive stages within the IGCPunit. This means that the gas travelling through the first stage of theunit and approaching the second launch point will be virtually unchangedas regards its fine dust content, but it will be almost fully cooled.The high centrifugal forces both at the bend which is just upstream ofthe second launch point and at the next bend which forces the gasesthrough the scrubbing fluid that has been launched from the secondlaunch point will cause the fine and still dry dust particles to crossand re-cross through the gas stream, greatly increasing the masstransfer and chemisorption of the dibenzo furan, PCB and related vapoursonto the dust.

Obviously, with only partial removal of the dust at each subsequentlaunch, this enhanced mass transfer will continue through each stage.However, this mass transfer process will be to steadily decreasingamounts of dust. It is therefore envisaged that further fine dust can beadded upstream of the IGCP unit (preferably, a dust which is much moreeffective at removing these vapours).

5.1.3 Application to Other Off-Gases and Dust Emissions

The application of the IGCP unit with other off-gases and dust emissionsis obvious to persons skilled in these areas. However, what may not beso obvious is the range of opportunities for cost reduction and problemsolving which emanate from the major size reduction embodied within theIGCP units in relation to equivalent capacity alternative technologies,which have equivalent dust removal or gas cleaning capabilities.

In particular, especially within the iron, steel and other furnace andkiln related industries, the size enables the dust and other contaminantremoval equipment to be brought close to each individual source ratherthan for it to be sited at the end of a sequence of collection ductworkor other infrastructure. This can enable major savings to be made onextraction and ventilation systems.

5.2 Formulation of the Abrasion Resistant Composite

5.2.1. Introduction

Silicon Carbide was chosen in this application because of its thermalconductivity, its availability, its uniformity, its chemical resistanceand its virtually unsurpassed abrasion resistance. Silicon Carbidecoarser than 10 mesh tended to break down and crumble within itself whenit was subject to severe impact. The uniformity and aspect ratio of thematerial was also important and specifically selected sources werechosen so as to obtain particles which had relatively equal dimensionsin each of their three characteristic dimensions and which hadrelatively closely defined size distributions within their commerciallyavailable and marketed size ranges. It was found that particles that areelongated in one or more directions were significantly less resistant toimpact and could not be compacted to achieve the necessarily low resinto filler volumetric ratios. This reduced compaction resulted in thewear properties not being able to be exploited to the full.

Silane pre-treatment of silicon carbide however improved the wetting ofthe particles, with the resin. This results in improved abrasionresistance of the material, improved impact resistance of individualsilicon carbide particles within the product, improved tensile strengthand it helps to reduce the strength loss and other problems which resultfrom the hydrolysis of the resins during use.

In order to obtain optimum results, the silane was diluted andpre-hydrolysed for about 1 hour. The optimum solution composition forthis process was 1.5% by weight in a 9:1 blend of alcohol and distilledwater. For optimum results, it was found that the silane concentrationshould not exceed 5%. The silane solution had to be prepared just priorto use because on standing there is an unwanted formation of siloxane insolution. The silane loading for optimum composite properties wasdetermined experimentally and the optimum was found to be as follows per100 kg of silicon carbide. Mesh SiC Water (litre) Ethanol (litre) Silane(litre) 10 0.80 7.20 0.4 24 1.00 9.00 0.55 60 1.44 12.96 0.72

A key feature of the development process for these optimum silanepre-treatment solutions was the creation of a solution that did notcause the silicon carbide particles to agglomerate as they were dried.Water is necessary to assist the bonding process between the silane andthe silicon groups in the silicon carbide. Surface tension and otherproperties of the solution result in agglomerates forming during thepre-treatment process especially with the finer particles. Thedevelopment process created solution formulations and product agitationmethods during the drying process which successfully overcomes theproblems of agglomerated fine filler particles within the final resinand filler mix, whilst at the same time achieving optimum strength anduniformity of bonding between the filler and the resin.

5.2.2. Particle Size and Size Distribution for the Silicon Carbide

In essence, the mesh size can be converted into micron size. Based onthis micron size, the optimum ratio of particle sizes for maximum inputof filler per unit total volume of composite will be in ratios of sevenbased on the micron size. Both bimodal and trimodal systems wereassessed. The trimodal system had large amounts of fines that mademixing and application of the composite very difficult. The bimodalsystem was therefore chosen for most of the mixtures.

The 8 mesh silicon carbide is a relatively large particle that isdifficult to support adequately in order to prevent it from crackingwhen it is impacted. The original formulations were based on acombination of 10 and 24 mesh (which is a formulation which is close tothe theoretically ideal for packing of 7 to 1 size ratio). However,moving to a combination of 10 and 60 mesh gave significant advantages asregards both abrasion and impact resistance. This improvement wouldappear to result from improved cushioning around each 10 mesh particleas a result of the finer infill particles.

Optimum packing density was researched using measuring cylinders and theresults were used to identify a mixture with good mixing and flowproperties and which had a near maximum input of solids. Mixtures of 10mesh solids with 60 mesh solids were found to be optimal. With meshsizes where the respective mesh numbers were larger than 10 and largerthan 60 (i.e. smaller micron sizes) the resin and solids slurry wasdifficult to work.

5.2.3. Resin Selection

Dow manufactures vinyl ester resins that are well known for theirchemical resistance qualities. For the Sinter Process gas scrubbing amaterial that can operate at 160-180° C. was needed. Dow produceDerakane 470 Turbo which meets both the temperature requirements and thechemical resistance requirements.

A component made, using this resin and maximum loading of siliconcarbide filler (using the above referred silane pretreatment and the 10plus 60 mesh mixture of particle sizes) was subjected to thermal shocktesting (six cycles of heating it to 180° C. and immediately dropping itinto a container full of cold water). The material did not show anysigns of cracking or other forms of degradation and the silicon carbideremained fully bonded. It was also noted that the material has differentmechanical properties at elevated temperatures relative to when it is atambient temperatures. At high temperatures, it is slightly elastic whichwill assist the overall abrasion resistance.

The following technique was developed to further improve the apparentelasticity of the resin and hence the overall abrasion resistance. Thiswas to include within the overall mixture or within specific parts ofthe product moulding where the properties are appropriate or preferable,hollow or sponge like fine particles so as to impart a degree ofelasticity and overall sponginess to the resin. These particles need tohave sufficient chemical resistance so as not to be degraded by theenvironment and they need to be small relative to at least the largerfiller particles and preferably they should be small relative to thesmaller (80 mesh) filler particles. Suitable hollow and sponge likeparticles include hollow glass spheres and both hollow and sponge likekaolin particles.

The purpose of these compressible inclusions is to create a morecushioned surround for the hard abrasion resistant fillers which willhelp to prevent them becoming cracked as a result of impact.

In most of the reported high temperature experience using Derakane 470Turbo, especially for those applications where ducting and containmentsystems carried gases where their bulk temperature was in excess of 220°C., the performance of the resin was improved by incorporating about 20%by weight of graphite into the corrosion barrier layer of the ducting orcontainer. This graphite greatly increases the thermal conductivity ofthis layer and thereby prevented a significant temperature gradient andhence thermal expansion derived stress gradient across this layer. Byremoving this stress from the surface, the normal early failuremechanisms of blistering and cracking which result from distress andfailure in the resin itself can be avoided/greatly delayed, therebyenabling good service life to be achieved.

Silicon Carbide has a similar thermal conductivity and expansioncoefficient to those of graphite and with silane pre-treatment it hassuperior wetting and bonding. With the greater filler content and thebenefit of the smaller 60 mesh rather than 24 mesh fine component thebenefits that can be derived from the graphite inclusion can be at leastreplicated and in general improved using silicon carbide. Where trimodalsystem is used, where the third component would be about one eighth toone tenth of the size of the 60 mesh, even better results are achieved.

This is a most important feature especially in the feed area of the IGCPunit where cool liquid splash on to hot surfaces will be an issue,especially in the area where the scrubbing fluid first hits the outerwall of the unit.

5.2.4 Further Refinements

It is envisaged that as a further refinement and where abrasion, impactand/or tensile as well as temperature properties are required, hollowglass, kaolin or other micro particles could be substituted or partsubstituted for the fine third component in a trimodal mix or can beadded as needed to a bimodal mix. Here the thermal conductivity of theglass, kaolin or other micro material will in general be less than thatof silicon carbide of graphite, but its inclusion will enable thenecessary additional cushioning to be achieved around the largerabrasion resistant filler particles. Also, because these hollowparticles are generally smooth and reasonably spherical in shape, theyshould proved good lubricity between the other filler particles, therebyimproving the flow properties for given filler content. This in turnmeans that more filler could be added for a given workability.

It is envisaged that this latter feature would be important if thetensile properties are important in that part of the moulded product.Typically trimodal systems would be needed if the tensile propertiesneed to be enhanced without reducing the impact, compression andabrasion properties. However, trimodal systems are generally moredifficult to work. Adding spherical or near spherical micro solids wouldassist the resolution of this workability constraint withoutsignificantly affecting the temperature and thermal shock issues.

As a result of all the test work and development, it is clear that forrealistic mixing and transfer of the mixed composite to the mould, theoptimum impact and abrasion resistance for a hard resin system such asDerakane occurs at the maximum bulk density on a bimodal system wherethe particle size is sufficiently different such that the micron size ofthe larger particles is divided by that of the smaller particles andproduces a ratio of around 9 to 10 whereas the theoretical ratio formaximum packing density is from between 6 and 8, preferably 7. Thepreferred mixture utilised 10 mesh with 60 mesh, which are approximately1950 micron and 200 micron respectively. These grades are approximately9.5 times different in size. This difference in preferred sizes foroptimum mixing, transfer, moulding, impact resistance and abrasionresistance, relative to the theoretical optimum for maximum packingdensity is an important feature which is critical to both themanufacturing process and to the product's performance. The benefit ofthis 9.5 ratio has been clearly demonstrated by the almost 50%improvement to the wear life for a polyurethane and silicon carbidecomponent where the ratio was adjusted from about 7 to 9.5.

Similarly, the benefit of optimally conducted silane pre-treatment ofthe silicon carbide prior to its inclusion creates a similar level ofimprovement to the impact and wear life.

In addition, it was found that approximately equal quantities by mass of10, 24 and 60 mesh silicon carbide or other mixes of 10 mesh and 60 meshsilicon carbide with much finer particles of silicon carbide or hollowmicro particles within both Derakane 470 Turbo and Polyurethaneconstitutes a trimodal system which has proven improvements to thetensile properties whilst retaining abrasion and impact resistance. Itis envisaged that this mixture could be used in areas that are not undersuch severe abrasion but need the tensile strength and impact capabilityfrom longer debris or objects in areas such as for support arms andfins, blades or hub spokes.

6. Detailed Description of the Equipment and its Applications

The preferred embodiment and application will be described, indicatinghow the carrier vessel and its contents can form part of an overallprocess system, with reference to the accompanying drawings.

FIGS. 1 and 2 illustrate diagrammatically 1% and 25% throughput pilotplants while FIGS. 3 to 32 illustrate in technical detail the IGCP unitand its various components and related equipment.

FIG. 1 illustrates a 1% throughput pilot plant incorporating an IGCPunit in accordance with the invention. The pilot plant 1000 incorporatesa dirty gas stream feed line 1001 feeding into a scrubber vessel 1002,having water nozzles 1003 providing spray water onto a turbulencecreator 1004 located within the scrubber vessel. The water is fed to thewater nozzles 1003 via a water pump 1008 feeding water from a water tank1005.

The scrubbed gas is fed through a liquid ring vacuum 1006 to a stack1007 from where it is released to atmosphere.

FIG. 2 illustrates a 25% throughput pilot plant incorporating a set ofIGCP units in accordance with the invention. The dirty gas stream 2003is fed through a flow control valve 2001 via a fan 2002 to the scrubbervessel 2004. Water is pumped from a water tank 2009 by means of a waterpump 2010 to the scrubber vessel 2004. The water is sprayed via waternozzles 2005 onto a set of multiple turbulence creators 2006 in for theform of the IGCP units.

The scrubbed gas 2007 is released to atmosphere via a stack 2008.

FIG. 3 illustrates equipment associated with one IGCP unit in accordancewith the invention and with a centrally arranged scrubber fluid feed.

Scrubbing fluid enters the equipment via a header 1. The fluid is drawnoff the header 1 at each IGCP unit through a standard moulded andlocated off take fitting 2. There is one fitting 2 per IGCP unit Eachheader 1 typically services two rows of IGCP units.

Feed to each IGCP unit turns through 90° and is directed downwards on toa centre feed distributor 6. A centre feed pipe 5 is centred, using aspoked hub 3, which in turn is held in place by an outer ring 4.

Scrubber fluid flow is directed radially outwards by the conicallytopped, centre feed distributor 6. The shape of the feed distributor 6is such that providing the feed pipe is located reasonably centrallywith respect to the distributor 6, it will distribute the scrubbingfluid uniformly around the perimeter of the distributor.

Lines 7 show the approximate profile of the scrubbing unit fluid as itflows across an annular gap. The upper straight line represents the flowof scrubbing fluid when the gas flow has been turned off (i.e. duringthe rinse off of any concretion) and the lower curved line shows thenormal curved flow with the gas flow on.

An annular flow profile is made up in this instance of 5 launch points,the first one being from the distributor 6. It is envisaged that more orless points can be arranged by using more or less of the following styleof components.

Typically, but not necessarily, the outer casing ring pieces 8 areidentical, thus simplifying component manufacture.

An inner core piece 9 has a similar profile to that of the remainingsection 10 of the distributor 6. It is envisaged that, for simplicity ofmanufacture, the profile for part or all of the unit can be the same.However, in order to maintain a steadily enlarging flow profile so as tomaintain a uniform gas velocity through the unit, the detaileddimensions of piece 9 do differ slightly from those of section 10. It isenvisaged that, in an alternative arrangement, the profiles on the piece9 and the section 10 can be identical and the casing rings 8 can beadjusted so as to be able to create the steadily enlarging profile,which is ideal. This option is illustrated in FIG. 32 where the righthand side of the figure shows the multi-component style for the casingrings 8 and an optional single component casing 34 which the combinationof the tapering profile and the casting techniques (referred to insection 5.3 above) makes possible. The tapered profile, in mostinstances, enables the casing rings to pass over the core pieces. Insome applications, it may be more important to have a larger axialoverlap between successive core and casing launch points and it may notbe possible to assemble or withdraw item 34. In these circumstances adifferent casting and/or assembly technique will be needed, such as thatshown in FIG. 3 or FIG. 31.

It is envisaged that, below piece 9 in FIG. 3, one or more further pairsof core and casing rings could be inserted in order to create morelaunch points per unit. In this embodiment, only one item 9 is shown,located on top of the core piece 11, which makes up the centre of thespinner section. This section includes in this embodiment six spinnerblades 12 which in turn are contained within the outer casing 13. Thewhole of 11, 12 and 13 are cast as a single component, but it isenvisaged that they can be made separately and assembled and bonded orjointed together from the individual components. It is further envisagedthat item 11 can be made from more than one piece and either assembledinto a single component or the individual pieces can be ‘O’ ring orotherwise jointed together. Alternatively, the casting techniquediscussed in section 5.3 can be exploited to create a single componentunit as shown in FIG. 27, or separate groups of components could be madeand assembled.

At the bottom of the spinner there is an inner skirt piece and hollowrecess 14 which serves to create the annular calming zone for the gasand scrubbing fluid flow as it emerges from the spinner blades 12. Thehollow recess prevents scrubbing fluid from accessing the central vortexand thereby accessing the gas outlet, as well as houses the boltingarrangement and its cover, which in turn holds the whole of the coreassembly together, by means of a nut 15.

The nut 15 has a loose anchor plate and a number of Bellville washers,alternatively, equivalent means of maintaining a steady tension on thetie bar 16 so as to maintain pressure on the “O” ring or equivalentseals between the core pieces during warm up and cool down. A domeshaped cap 17, which is sealed into the hollow end of 14, covers the nut15. In this instance, the cap 17 is held in place by an “O” ring, whichis secured by a light coil spring. This coil spring is arranged outsidethe nut and washers 15, but it could be between the nut and the cap 17.

The other end of the tie bar 16 is located in the top core piece 10using a nut welded to an anchor plate 18. The top of the plate 18 has adomed cap fitted to it so as to prevent the resin mixture from fullyencasing the anchor plate and nut, thus enabling the effects ofdifferential expansion to be absorbed without putting excessive tensileforces into the internal structure of the resin.

The outer casing of the spinner section, 13, extends below the spinnerblades for a minimum distance so as to provide a suitable wear surfacein the immediate high wear area, which occurs immediately beneath thespinner blades. This extension also ensures that the joint with the nextwear ring 19 is kept clear of this high-wear area.

Wear ring 19 in turn sits on the top of the main cyclone body section20. The top of this section has a shaped shoulder and locating lug 21,which sits on top of, and is O-ring sealed to the mounting ring 22. Themounting ring 22 is resin bonded onto and sealed to the punch plate 23which is sealed into the main carrier vessel into which the IGCP unitsare mounted. This punch plate 23 is supported by support beams 24, whichtypically are arranged between each row of IGCP units.

At the bottom of the cyclone section 20, there is a vortex finder pipe25, which delivers the clean gas to the clean gas outlet 26. The wholevortex finder assembly is spigot-and-socket mounted onto the end of thecyclone section 25, using the joint 27.

The part rings 28 at the bottom annulus 33 are arranged so that thebaffles 29 are about 35% of the way around the underside of therespective ring in the direction of rotation.

The scrubbing fluid outlet 30 is drained by gravity into a collectionpipe 31. The outside of pipe 30 is equipped with a vibration absorbingring 32, thus preventing excessive wear on the outside of the pipe as aresult of vibration at this end of the IGCP unit.

The whole arrangement of the collection pipe 31, the IGCP units, thepunch plate and the drainage collection pipes are typically arrangedinto an overall carrier vessel with the dirty gas entering the top ofthe vessel and the clean gas extracted from the side of the vessel at aconvenient point below the punch plate 23.

The lower part of the vessel receives the scrubbing fluid, which isdrained via the collection pipes 31. This lower part of the vesselprovides a suitable storage and recirculation vessel from which thefluid is pumped back to the scrubber fluid inlet header.

Such an arrangement is shown diagrammatically in FIG. 12 and is referredto in more detail when that Figure is discussed below.

FIGS. 3 a and 3 b show the above details at a larger scale.

FIG. 4 shows a side elevation of the same details as are shown in FIG. 3a The scrubber fluid feed pipe is shown in section (40) with the offtake saddles 41. The right hand off take saddle leads to the IGCP unitshown and the left hand one would lead to an IGCP unit (not shown),located to the left of the IGCP unit shown.

Each saddle piece 41 has a chamfered flat area at the top and bottom.The lower chamfered area, in combination with that of its oppositeneighbour forms a flat surface, which enables the scrubber feed liquorpipe 40 to rest on a loose fitting cover (not shown), which in turnrests on top of each ring 47. The dust cover has holes in it, the holesbeing aligned with and of a similar size to the entry diameter of thetop of each ring 47 on the IGCP unit. A typical dust cover is shown inFIG. 10 and a typical arrangement for the feed pipes 40 and off takesaddles 41, which would go with the dust cover arrangement, is shown inFIG. 6.

Inserted into each off take saddle 41 and “O” ring sealed to it is afeed pipe 42. The feed pipe 42 has a bellows arrangement within it tocater for any necessary movement or adjustment associated withdifferential expansion and other flexing or construction toleranceissues.

The feed pipe 42 has a side inlet 43, which is orientated such that itsopen end is directed towards the flow in pipe 40. This orientationensures a uniform amount of fluid drawn off by each off-take,irrespective of the steady fall off in velocity along the header pipefrom the header inlet to the last feed pipe in the row.

The feed pipe 42 is connected to the vertical feed to the IGCP unit 45,by the on site assembled and pegged joint 44, developed and machinedfrom solid PTFE for on site assembly and disassembly without the needfor threaded fixings. This design avoids the problems of thread bindingand corrosion in corrosive and hot environments. FIG. 7 presents anenlarged view of the inlet arrangement and the joint 44. FIG. 8 presentsan exploded view of joint 44.

The vertical feed pipe (87 in FIG. 8) is held upright and central by acentre feed boss 45 and its support spokes 46. The spokes 46 are mountedin a top casing ring 47, using a flexible arrangement that allows fordifferential movement between the spokes 46 and the ring 47 during warmup and cool down. This assembly is shown in greater detail in FIG. 9.

Mounted on a shoulder on the outside of ring 47, is a suitabletemperature and corrosion resistant, flexible ring 48. Alternate IGCPunits (not shown) are fitted with these rings and the ring fills the gapat the touch joints between each IGCP unit when they are arranged ontheir punch plate mounting. This ring 48 acts as an anti-vibration andseparating packer between each unit.

Ring 47 rests on and locates itself with respect to the casing ringbeneath it (item 8, FIG. 3) using a shoulder 49. The shoulder 49incorporates a necessary sealing member, in the form of an O-ring. Thisarrangement is used to locate and seal each casing component on to theone beneath, all the way down to the top of the cyclone body piece (item21, FIG. 3).

The core rings are also located on to and sealed to each other in asimilar manner using a shoulder 50, which is the same or similar foreach core piece.

Stepped edge launch points for the scrubbing fluid on the radiallyinwards launch 51 and the radially outwards launch 52 are also shown.The profile of the stepped edge is shown in more detail in FIG. 5 atitem 60. The vertical face of the step has a slight taper to facilitatemould release when cast. The angled face of the stepped edge 60 has asimilar angle as the upstream sloped face of the profiled core piece.

The equivalent stepped edge on the casing ring has similarly slopedfaces.

The corner between these two sloped faces of each stepped edge has afillet radius, for simplicity and robustness of casting as well as toensure maximum effect from the swirl and scouring action from the backeddy, which is encouraged within the stepped edge.

The sizing of this stepped edge is somewhat of a compromise between theeffectiveness of scouring action and making enough allowance for wear inthis high abrasion area. Typically the step should have a similar depthand width and this should be between 0.5 and 2.5% of the outsidediameter of the annulus.

In addition to the optimal dimensions of the stepped launch edge, thereare a number of distinct advantages which can be gained under specificconditions by changing the relative sharpness of the step. In FIG. 5,the stepped launch edge is shown as having a near vertical face(actually, it is sloped slightly for ease of moulding in this detail).However, for optimum functionality, the near vertical face shouldundercut the launch surface. From the perspective of achieving theminimum percentage of scrubbing fluid dribbling down the face, the anglebetween the face and the launch surface needs to be as acute aspossible. From the perspective of robustness to accidental damage priorto component insertion, to impact from debris whilst in service and togeneral wear, the angle needs to be similar to that which is drawn inFIG. 5. Once the angle between the face of the step and the launch faceexceeds about 150°, then the effectiveness of the step starts to becomeimpaired.

The angle of the lower face of the step is less important, providing ithas a similar slope to that of the launch face or it slopes furtherdownwards (away from) the launch step. Once the angle between the launchface and this lower face exceeds about 15° upwards or about 30°downwards from the angle of the launch face, then the performance of thestep starts to become significantly impaired.

The optimum value for the radius 60 is between 0.5 and 1.0 times whatwould be the length of the face of the step if there were no radius. Atradii which are less than 0.5 times this length the performance of thestep starts to become impaired. At radii which are more than about 0.9times this length, there is not much room for wear to take place beforethe angle of the effective face starts to become significantly affected.

FIG. 28 shows a design of step which represents a practical compromisebetween all the above criteria. It also enables the launch edge to be asnear to the corner of the flow profile as possible, a) to get maximumfluid velocity at the launch and b) to minimise the flight distance fromthe point of launch to the far side of the flow profile for a givenwidth of annulus.

Also shown in FIG. 5 is the stepped or overlapped joint arrangementwhich is used to ensure minimal scouring of all the body joints betweenthe casing and the core components. The width of this step or overlap isselected to suit the particular conditions that relate to thatparticular joint.

A typical “O” ring joint and component location details are shown at 62and 65 respectively and at 63 and 64. It will be noted that there is aclose tolerance fit between each component and the one beneath it so asto ensure proper alignment of the water distribution piece (item 6 inFIG. 3) at the top of the core pieces with the scrubber fluid inlet pipe(item 5 FIG. 3).

Item 66 is the centre tie bar (or threaded rod) which is used to holdthe core assembly together.

FIG. 6 shows a typical detail for the scrubbing fluid distributionsystem together with the segment of the overall carrier vessel withinwhich it is convenient to mount this pipework. It will be noted that thearrangement involves no bolted or other forms of clamped jointing withinthe vessel. This ensures that maintenance work cannot be delayed as aresult of the binding of threads on bolts or other screwed fittings.

The vessel section 72 is jointed to the neighbouring vessel section viaa flange or some other suitable form of connection 70, and to the inletducting for the incoming gas at the connection 71.

Each header pipe is arranged such that it has an outlet connection (suchas a flanged connection) 74 and an inlet connection 73. Preferably, theoutlet connection should be fitted with a restrictor plate clampedbetween the flanges (or other form of joint arrangement) and should bepiped on back into the recirculation reservoir at the bottom of thecarrier vessel. The restrictor plate should have small holes at both thetop and the bottom of the pipe. The holes should be at least 2.0 timesthe largest aperture size in the screening device that should be fittedto the pumped re-circulation back to the IGCP unit inlets. This willeffectively prevent all potential for blocking these holes.

The function of the top hole is to enable any gas, which gets into theheader to be freely vented. The function of the bottom hole is to enableany solids, which accumulate on the bottom of the header pipe to beflushed clear on an ongoing basis rather than to accumulate andpotentially concrete them together or to the pipe wall.

The individual pipes between the flanges 73 and 74 should be built intothe vessel wall section 72 so as to ensure that they are always properlyaligned with respect to the IGCP units.

The arrangement of saddle pieces 41 (FIG. 4) is shown at 75. Thisarrangement is appropriate to suit the arrangement of IGCP units shownon FIG. 10. Obviously the pack of IGCP units can be smaller or larger assuits the particular application.

FIG. 7 shows the arrangement of these saddle pieces and the connection,which fit into the saddles and feed each IGCP unit. For clarity, thenumbering of these components is different to that in FIGS. 3 and 4.

In this detail, the position of the dust cover 81 is shown beneath thesaddle pieces 82 which are bonded to the header pipe 83. The inlets 84to each IGCP unit connector bellows piece 86 are shown, together withthe three O rings 85 at the sealed joint between the saddle and the IGCPunit feed. The three O rings are arranged such that the connector canslide in and out of the header pipe saddles as necessary to absorbmovement and differential expansion in the axial direction. The centre Oring is intended to provide the sealing, the outer O rings are there toprevent dust and grit ingress and to assist the centralising of the Oring arrangement whenever the bellows is under a bending strain as aresult of movement in other than an axial direction.

The IGCP unit feed pipe 87 is arranged to be inserted down into the topof the IGCP unit feed boss (45 on FIG. 4) once the inlet to theconnecting piece 84 has been inserted into the respective saddle 82. Thelower and upper O rings 93 and 94 in the body of 87 seals the feed pipe87 into the hub at the outer end of 86.

The feed pipe 87 has a radial feed machined or cast into it which isorientated (using peg 88 or another tool inserted into the hole 90) suchthat it is in line with the hole through 86. Opposite the inlet hole in87 there is a blind socket into which fits the plug piece 89.

This plug piece serves two purposes. Firstly it closes the hole throughwhich the bellows 86 and the inlet 84 were machined or cast. Secondly itlocates with the blind socket in 87 to locate 87 both vertically and inorientation.

Plug 89 is then sealed using O ring 92 and held in place with the peg88. There is a hole 91 in the rear of plug 89 which can be used toorientate the plug 89 such that the hole for peg 88 is correctlyaligned.

During dismantling either peg 88 or a suitable tool (e.g. a thin bar orscrew driver) can be used to pull plug 89 out using the hole 91 as themeans of gripping the plug.

Similarly, the feed pipe 87 can then be withdrawn using the sametechnique, using hole 90.

For clarity, FIG. 8 shows in section an exploded view of the componentsmaking up the IGCP unit feed. The same numbering as in FIG. 7 is used.

FIG. 9 shows the preferred arrangement for the feed boss and its supportring (46 and 47 respectively on FIG. 4). For clarity, the referencenumbers on FIG. 9 are as follows. The Feed Boss is made up of a centralhub piece 102 on to which are cast (in this instance 4, but 2, 3 or morewould be acceptable) spokes 101. These spokes are mounted into the ring107 using slots 108.

These slots are arranged such that an elastomeric filler is insertedinto the gap 105 in such a way that the radial gap 106 is not filled.The reason for not filling the gap 106 is to enable the elastomericproperties of the filler in gap 105 to allow the spokes to expand duringstart up and to shrink during cool down at a greater rate than that ofthe ring 107 without causing too much stress to be applied to 107. Thisfeature is unnecessary when the IGCP unit is to be used in situationswhere the temperature of the incoming gas is relatively close toambient. However, in situations such as with Sinter Off-Gases, thisfeature is considered to be important if relatively simple heatresistant mouldings or castings are to be utilised.

The curvature 110 of the ring 107 has been specifically arranged so asto provide optimum entry orientation for the gases around the centre huband on to the scrubbing fluid distribution cone (6 in FIG. 3).Similarly, the shape of curve 111 has been arranged so as to create thenecessary profile to receive the scrubbing fluid flow during the “gasoff” condition and the normal running condition as described for thetype a) feed arrangement.

The shoulder 109 is where the elastomeric spacer and vibration absorbingring (48 on FIG. 4) is mounted.

The corner 112 is arranged to create the necessary abrasion resistingoverlap on to the first casing ring (8 on FIG. 3). The spigot piece 113is arranged to trap the O-ring seal (not shown here) between this pieceand the first casing ring. This spigot also has a closely toleranced fitto the outside of the casing ring, so as to enable the whole IGCP unitto be aligned within it.

In order to enable the effects of differential casting shrinkage andheat treatment shrinkage to be overcome, the central hub 102 can be castwith a machinable insert 103 arranged in its centre. This enables thestandard heat, chemical and wear resistant formulation to be usedthroughout the construction (except for 103) and once the elastomericinfill 105 has been inserted, then the hole for the feed pipe can bebored using the location face of the spigot 113 for its centring.

FIG. 10 shows a loose cover, which fits over all the IGCP units andserves to prevent as much dust as is reasonably possible from accessingthe gaps between the IGCP units. This is to assist maintenance. Thecover also serves to provide a flat surface upon which the scrubberfluid inlet header pipes can rest. The holes 119 in the cover 118 arearranged so that they align with the inlets to each IGCP unit.

FIG. 11 shows the punch plate mounted support rings which support eachIGCP unit and which enable each IGCP unit to be sealed to the punchplate and hence into the main carrier vessel. The lower wear ring 19 ofeach IGCP unit sits on and is O ring sealed to the shaped end 21 of thecyclonic tail pipe body 20. This shaped end 21 is in turn sealed usingtwo O rings 35 to the support ring 22. Each support ring is built intoand sealed to the punch plate 23.

In this sectional view, the punch plate is very narrow, but it of courseoccupies the remainder of the floor area in between the individualcircular support rings. The design and mounting of these rings into thepunch plate is shown in FIGS. 17 and 18 respectively.

The punch plate is supported by support beams 24 which are built intothe underside of the punch plate 23. The means of orientating thesebeams so as to enable the close tolerance construction of this wholepunch plate and support ring assembly is shown in FIG. 18.

FIG. 12 shows a diagrammatic sectional arrangement of all the componentsand equipment referred to in this specification within a carrier vessel.The position of the dust cover is shown at 120. 121 is an inspection andaccess cover within the main gas inlet duct. This duct is shown comingin from the top, but clearly it can be arranged to come in from the sideif the overall plant layout so requires.

The scrubber fluid feed header and an individual feed pipe is shown at122.

The carrier vessel is arranged such that the part of the vessel with thescrubbing fluid feed header (FIG. 6) and the next section down (FIG. 25)complete with the punch plate and a full set of IGCP units and punchplate drains (FIG. 23) can all be lifted out as a single unit and areplacement complete package can be lifted back in as a single assembly.In order to enable this single entity to be guided into its correctorientation with respect to the scrubbing fluid outlet connections fromeach tail pipe, guideposts 123 are arranged with a close fit to theconnecting flanges (or other connecting arrangements) on the carriervessel. There will also be location lugs on the outside of thisone-piece assembly which will orientate the assembly with respect to thescrubbing fluid inlet pipework.

These guide posts or other means are also used as a means of supportingthe upper and lower walkway accesses (138). This enables all thenecessary connections to be made and removed without having to disturbany external pipework or infrastructure.

These same guideposts also serve to locate the gas inlet ductwork andexpansion hood as that is replaced following such a lift out of the oldand lift in of the replacement operation.

This whole mechanism and the integrated nature of this design has beenarranged to enable down time to be minimised. It is estimated that thewhole of a vessel's IGCP units should be able to be exchanged and forthe whole vessel to be back on line again within less than a shift byusing this arrangement.

The position of the gas and scrubbing fluid contacting part of one ofthe IGCP units is shown at 124 and the vortex finder area of another at125, together with the gas outlet from that other unit at 126.

At 127 the floor support beams are shown which support the loose fittingfloor plate (FIG. 22) which provides the access to and the support fromthe pipe drains 132 and punch plate drains 133 (FIG. 23) which drain theused scrubbing fluid from each IGCP unit tail pipe into the lower partof the carrier vessel.

The normal liquid level for the scrubbing fluid in this lower part ofthe vessel is shown at 128. The scrubbing fluid off take to there-circulation pumps is shown at 129.

Typical vessel support arrangements are shown at 130, but there are anumber of different methods of support which can be used.

The cyclonic section of one of the IGCP units is shown at 134 and thepunch plate support for the IGCP units is shown at 135.

At 136 is shown the location for the entry of a supply of scrubbingfluid to flood the top of the punch plate.

This supply of cool scrubbing fluid performs a number of duties. Firstlyit ensures a gas tight seal between all the IGCP units and theirmounting into the punch plate support rings. Secondly it keeps this areaof the construction beneath the dust cover cool when hot gases are beingscrubbed. This enables heat distortion problems within the punch plateand its support to be avoided. It also enables lower temperaturecapability resins to be used for the construction of these components.This can have a significant effect on costs.

At 137 is shown one of the scrubber fluid inlets to the feed headers.

FIGS. 13, 14 and 15 show in more detail the construction and arrangementdetails for the tail pipe vortex finder area. These details also showthe locations where abrasion resistant materials or finishes arerequired. The same component numbering is used for all three Figures.

The cyclonic section 20 is connected at spigot or other form of joint 27to the vortex finder assembly. The vortex finder pipe 25 dischargesthrough the partial bend at 26 and the gap between 25 and 20 forms theannular section 33. The rings 28 form a square end to this annularsection which enables the used scrubbing fluid to be separated from thegas and discharged via pipe 30.

In order to achieve this separation, the scrubbing fluid with someentrained gas passes through the gaps 34 between the annular ring pieces28 into the space below the rings. Here (and within the annular spacebeneath the rings) the radial baffles 29 (which project across the fullwidth of the annulus below the ring pieces 28) stop the rotationalmovement of the scrubbing fluid and entrained gas. The scrubbing fluidfalls to the bottom and exits via pipe 30.

Section AA on FIG. 14 shows a radial infill piece beneath the end of oneof the ring pieces 28. This infill closes the gap between the top of theinclined end plate which is formed around the gas exit 26 to close offthe annular gap below the ring pieces 28. This infill (as shown insection AA) prevents the non uniform annular space that is formed by theoutlet 26 and the inclined end plate from upsetting the performance ofthe vortex finder.

FIG. 16 shows a detail of the body of the cyclonic section of the IGCPunit (20 in FIG. 3). The body is referred to here as item 200, and thesupport and location shoulder is 201. On the left hand side of thisshoulder is a triangular location piece 202, which in this design isshown as a piece which can be bonded on after moulding/machining. Otherattachment mechanisms would be equally suitable. The function of thislocating piece is for it to align with the scrubber fluid outlet pipe(30 in FIG. 13). This then aligns with the slot in the top of thesupport ring (213 on FIG. 17), which is mounted on the punch plate. FIG.18 shows how each of these slots need to be orientated on the punchplate as a whole. As a result of this detailing, a standard IGCP unitscan be put into any location on the punch plate without any need tospecifically orientate it and the outlet pipe for the scrubbing fluidwill automatically align with its respective pipe drain.

At 204 on FIG. 16, the outside diameter of the body of the cyclonicsection is shown as being machined/finished appropriately to enable itto be fitted to joint 27 (FIG. 13) without the outside diameter of joint27 becoming too large for it to fit comfortably through the support ring(FIG. 17).

The support ring (FIG. 17) has its main thickened structural cylinder210 finished on its inside surface suitably to create the required Oring seal. The tapered shoulder 211 provides a suitable lead in taperfor the O-rings on the outside of the IGCP unit body to slide into thenarrower bore of 210. The diameter at 212 is arranged to enable the IGCPunit to be entered easily into the support ring and for the O-rings notto be damaged as they pass the slot 213.

FIG. 18 shows a preferred arrangement for the jig that can be used tocreate the punch plate using the support rings (FIG. 17) and normal GRPlay up techniques. The jig has discs 221 (which are shown in the sideview at 232) over which each ring 231 is placed. Each disc is marked(224) so as to identify the required orientation of the location slots(213 on FIG. 17). In addition to discs 232, there will be discs 222 and223 for each style of punch plate drain. Drains A (222) are for normallevel control and drains B (223) provide emergency drainage capacity inthe event that, for example, a scrubber fluid feed header ruptures.These discs 222 and 223 may be thicker that discs 232 (as indicativelyshown at 233 in the enlarged part of the side view) so as to enable ahole to be formed within the GRP lay up which will enable the pipe 280(FIG. 23) to be inserted and then the flange 286 (FIG. 23) to be resinbonded into place.

The jig base plate 220 will have a circular ring around it 228 whichwill contain the GRP lay up and thereby create a circular plate whichwill fit snugly into the carrier vessel.

Detail X on FIG. 18 shows the mechanism by which the support beams canbe accurately located and held in place whilst they are bonded on to theunderside of the punch plate once it has been moulded and cured. At 225,the outlines of four carrier ring location discs are shown and at 227 isthe relative position, which will be occupied by a support beam. The topof the surface of the jig on which the punch plate is moulded will havea sequence of short blind holes drilled into it at 226, one each side ofthe support beam position. These will create short pegs on the undersideof the punch plate.

Once the plate has been formed and cured, the plate can be removed fromthe mould, inverted, and after the release agent has been removed in thearea of each support beam, these pegs can be used to accurately locateeach beam as the beam is bonded into place.

This detail enables very narrow beams to be used, which in turn enablesthe maximum number of IGCP units to be fitted into a given size ofcarrier vessel.

FIG. 19 shows the preferred arrangement for securing the tie rod, whichholds the core sections of the IGCP unit in place when a multiplecomponent assembly is used. In order to achieve the correct alignment ofall the components, they are assembled upside down on a centralisingjig. This jig will have a tube which will fit through the hole in thecentre feed hub 102 (FIG. 9) and locate the hub and hence the ring 107(FIG. 9). This tube will also locate and centre the end of the cone 6(FIG. 3). All the other components will then be stacked one on anotherand then the plate 244 will be fitted over the tie rod following by anappropriate arrangement of Belleville washers (or equivalent) 245 andnut 246.

The cover piece 248 could be inserted on to the top of spring 247 andpushed down hard so as to allow O-ring 249 to be inserted. The cover canthen be allowed to slide back so as to trap the O-ring and seal theinner end 243 of the hollow end 250 to the core of the spinner section.

Arrow 241 points to the hollow inner zone of the assembled core and 242indicate a clearance hole in the spinner section core piece.

Once the nut is tight, the outer casing pieces can be strapped orotherwise clamped together using straps or clamps which are orientatedsuch that they reside in the gaps between individual IGCP units oncethey are assembled.

These same clamps, or additional clamps should also be arranged tolocate on to suitable fixings on the outside of each carrier ring (FIG.17) so that each IGCP unit can be clamped into place and held upright onthe punch-plate.

FIG. 20 shows the preferred arrangement for securing the upper end ofthe tie rod 263. A nut 266 is welded to the plate 265 and a moulded cap264 is fitted over it so as to create a gap above the nut and above theplate 265. A sleeve 267 is fitted around the tie rod and inserted intothe mould component which will form the inner profile 262. The top corepiece and scrubber fluid distributor 260 can then be cast, including theO ring seal groove and locating face 261.

When the mould is released, the sleeve 267 should be withdrawn and thetie rod loosened so as to create a clearance between it and the insideof cap 264. The tie rod should then be resin bonded to 260 using the gapleft by sleeve 267.

FIG. 21 represents the inner and outer profiles of the style of spinnerblade which achieves close to optimal spin whilst retaining good wearand mouldability characteristics.

FIG. 22 shows the arrangement of the floor plate and support beams fromwhich the pipe drains and punch plate supports are assembled andsupported. The plate 270 is loose fitting and covers the whole floorarea. It is supported on beams 271 and has holes cut to suit the varioussized drains 272 that need to pass through the floor. The sizes forthese drains which are shown are indicative only and supply a nominal 4metre diameter carrier vessel.

The plate and support beams are carried on the vessel wall 273 usingnormal moulded in support ring 274 or their equivalent. Arrow 275 pointsto the vessel connecting flange which connects this part of the vesselto the section which houses the IGCP units. 276 is an indication of thelikely ring beam support for the vessel but other means of vesselsupport can be used. 277 identifies the gas outlet connections from thispart of the vessel.

FIG. 23 shows the two styles of drains. Pipe 280 is fixed to and bondedto the punch-plate using flange 286. It has a coupler 281 attached tothe lower section 282 and which O ring seals to the pipe 280.

Both types of drain have shoulder 283 built on to the pipe outsidediameters in such a position that when collet pieces 284 are insertedinto the holes in the plate 270 (FIG. 22), the pipes 282 and 288 aresupported at the correct height with their open ends 285 submergedbeneath the scrubber fluid at the bottom of the carrier vessel.

In the case of pipe 288, the flange 289 is provided purely to enable thepipe to be lowered down and rested on the floor whilst IGCP tail pipesare inspected, repaired, or whatever. A similar shoulder can be fittedto 282 if the coupler outside diameter is not large enough to provide asimilar function.

FIG. 24 shows the lower section of the main carrier vessel 290, thewalkways 291, guide posts 292, the gas outlet ducts 295 and the likelyadjacent carrier vessel and its interconnecting walkway 296 when morethan one carrier vessels are required for the specific duty.

FIG. 25 shows the typical detail for the part of the carrier vessel intowhich the main punch plate support is built. The main vessel wall 142has interconnecting flanges or other suitable jointing arrangements at140 and 141. The input connections for flooding the punch-plate withscrubbing fluid are shown at 143 and the support rings for thepunch-plate and its support beams are shown at 144. Whilst two inputs143 are shown, this is not essential. All that is needed is to achieve areasonably uniform flow of fluid across the plate to the drains whichideally should be diametrically opposite these feeds.

FIG. 26 shows an indicative process flow diagram for a typical gascleaning process. 301 represents the gas inlet duct, 302 provides anadditional supply of quench or wash down spray liquor should this beneeded. It should be noted that where dust concretion is a potentialproblem, this connection should not be used.

303 represents the main feed headers to the individual IGCP unit feeds304. The IGCP units are shown diagrammatically at 305, mounted on aflooded punch plate 306. The spinner section of each IGCP unit isindicated at 307 with the tail pipe of the cyclonic section at 308 andvortex finder liquid drain at 309.

310 represents diagrammatically the typical four vortex finder drainsinto one pipe drain 311 leading into the recirculating water reservoirof scrubbing fluid 320. 312 represents the feed to the punch-plateflooding inlet, while 315 indicates the feed pipe to the recirculationpump 314, which in turn feeds the return header pipe 313.

Similarly, 316 refers to the feed pipe for the solids and salts ladenpurge from the carrier vessel which leads to pump 317 and hence alongpipe 318 to the wastewater treatment or whatever downstream process isrequired. 319 refers to the solids thickening zone of the carriervessel, while 321 shows one of the punch plate drain pipes from one ofthe drainage points 322 with 323 and 324 showing the scrubber fluidmake-up and reagent input connections respectively.

The scrubbed gases leave via one or more ducts 325 to fan(s) 326 andoutlet duct(s) 327 to the exhaust stack 328 or to wherever the scrubbedgases are to be forwarded.

FIG. 27 shows the equivalent detail to FIG. 4 but with the maximumexploitation of the potential benefit from the casting and mouldingtechniques referred to in section 5.3. The numbering refers to the samenumbering that is used for FIG. 4 with additional numbers. 51 and 52 nowpoint to a type of launch step which can be produced using these castingtechniques and which cannot be reasonably produced when casting usingnormal re-usable moulds. These step details are shown in larger detailin FIG. 28.

Also shown in FIG. 27 is a single casing piece 54 which incorporates theessential profiles of the top ring 47 all the way down to the O ringjoint and location spigot detail 58 which fits on to the top of thecyclonic section shown here as 59.

In this arrangement, this whole casing section 54 is joined through thespinner blades (12 on FIG. 3) to a single core piece and liquid feeddistributor 55. As a result of creating this core piece as a singleintegral casting, none of the tie bolting is required and the hollowcore inside skirt 57 can now extend all of the way up through the unitat 56, to virtually the underside of the liquid distributor. This notonly greatly simplifies on site activities, it also ensures that allalignment issues between the core and the casings are completelyresolved and fixed permanently during casting.

It is also obvious that this construction, whilst more complex to castremoves a great number of specific and essential tolerance areas as wellas creating a somewhat lighter product.

In FIG. 29, the same structural concept as is shown in FIG. 27 is shownexcept that the reasonably maximum amount of thick sections within themoulding have been removed. This makes the mould formation a little morecomplex, as well as the casting process but it does create an evenlighter construction and a product which is more resistant to thermalcycling.

FIG. 30 shows a typical two launch points core component and the type ofmould arrangements that would be employed in order to cast it. Thecomponent is cast upside down so that the main wear areas (indicated bythe arrows marked 10) face downwards and outwards.

The typical locating spigots, sockets and O ring faces which enable thiscomponent to locate to and seal to its adjacent components when it issealed into an IGCP unit are shown at 15 and 16. Both of these areasrequire high precision and a high quality surface finish.

The central core of the casting 1 can be sleeved in plastic film(applied as a tape) or using a thin film of shrink wrapped plastic.Alternatively but less preferably normal mould release agents can beapplied.

This central core would be attached to a circular bottom plate 2 intowhich the detail for face 16 has been machined. In this illustration asocket head screw 3 is used for the location and fixing, but anysuitable arrangement can be used.

The plate 2 will have a spigot ring or other robust and rigid attachmentarrangement 5 by which it can be located and held within a two piece ormore piece mould body 4. This mould body would be keyed together foralignment and secured using a strap or ring 6.

At this level of assembly, a resin rich and fine filler mix would beapplied at 11 to create the necessary fine detail 16. Then a maximumabrasion and impact resistant mix would be inserted in layers into area12 and compacted to create a good surface finish and to expel all airbubbles.

At some point towards the top of mould 4, the feeding of this mix 12would be stopped, the top of the mould would be cleaned off and the nextsection of the mould 7 would be added and secured using the strap orring 8. Mould 7 would be located to mould 4 using a spigot and socketarrangement such as is shown in FIG. 14 or some other suitablearrangement.

The next area of the casting (13) has a much reduced abrasion and impactduty. It also has a relatively flat and poorly sloped top surface whichwill hinder the escape of air bubbles. The mix for zone 13 can thereforehave a lower abrasion resistance and greater workability. This can beachieved using either a greater resin content or a different blend ofcourse to fine fillers. A higher resin content would be the normalsolution, however, these components will be subject to heat cycling andthe material in 13 must behave in a similar manner to that in 12, and itmust conduct heat at a similar rate to that in 12.

A compromise mix for 13 is therefore required, having a high fillercontent similar to that of 12 with sufficient workability to create areasonable surface finish and air exclusion.

Once in the narrow section the mix and its application for 17 willchange again to the same mix as was used at 12.

Then mould 9 would be applied and held in place with ring 19 in the sameway as for mould 7 and ring 8. Then area 18 would be filled using thesame mix and technique as was used for 13.

Mix 18 would be applied up to a level of 1-5 mm short of the top of theproduct core piece 15. At this point, a new formulation 14 would need tobe applied which could be post machined in order to create the profile15. Mix 14 would be applied to a level of at least 3 to 4 mm above theprofile 15 so as to ensure that any air bubbles which may rise followingfilling will rise to a point just above profile 15.

The above description applies to a normal moulding technique. However“Lost Wax” types of techniques can also be employed. This technique canbe used to create much more complex shapes and would in general beneeded for the spinner section.

In the above example, the stepped edge to the launch point is able to becast using a split outer mould. However, for an equivalent casing ringor group of casing rings, this profile will require either the use of aseparate mould insert, a collapsible core or a lost wax technique. Inthis environment, collapsible cores are unlikely to have a tool lifewhich can justify their cost. The lost wax process would thereforeappear to be the optimum.

Derakane 470 Turbo resins require high temperature post cure and thisneeds to be carried out at successive stages. Particularly at the firststage, the dimensional stability of the moulded product is not good, butwith conventional release agents, migration of the release agent duringpost curing is common. This leads to mould release problems if theproduct is post cured in/on the mould. The choice of a “wax” which doesnot melt until the part is heated to the second and final post curestage will enable the product to be kept in shape during the critical(from a shape point of view) first post cure.

This concept then enables the whole IGCP unit to be created as a singlecasting using the above methodology and a sequence of lost waxcomponents as well as a sequence of external split moulds.

FIG. 31 shows a potential way by which this can be achieved.

The whole IGCP unit would be cast upside down with the centre feeddistributor cone 1 omitted. This feature would be necessary to enableany post cure distortions to be accommodated such that the point of thecone is central and the launch step on this feed distributor alignscorrectly with the inner receiving radius of the casing section 3. Thisfeed distributor 1 would be cast separately (as would the feed boss andits spokes) and located accurately and resin bonded in place once thefull post cure has taken place.

The moulds would be supported on a suitable base 2 into which would bemachined the top profile of the casing 3 including notches 4 for thespokes of the feed boss. Rigidly mounted on the base 2 would be a centrebar 5 upon which the whole assembly would be centred.

Moulding would proceed basically as described for FIG. 30 with the firstlost wax piece 9 being inserted once area 3 was part full. In thisinstance, there is no specific seal or other faces to be created andtherefore a resin and fines rich input (11 on FIG. 30) would not beneeded.

Then as mould filling progresses, the outer casing split mould 7 wouldbe added and secured by the tie or ring 8. This would be followed by thelost wax piece 6.

Filling would then commence on the core section as well as the casingsection.

Then the lost wax piece 11 would be added, followed by the split mould12 followed by lost wax piece 13 and then by core piece 14 followed by15.

The procedure would then continue in the same way up to the start of thespinner section. The 6 or 8 blades 16 will be created by assembling 6 or8 lost wax infill pieces 17 between each blade. These would slot intothe top of the last annulus lost wax piece 18 so as to locate them andthey would be secured above the trailing edge of the spinner blades witha tie or ring 19.

Once the spinner blades are completed, the inside of the wear ringsection and the top of the annular skirt lost wax piece 20 would beinserted. This could have a number of small tundish feeds and vent holes21 to enable the top edge of the skirt to be created using a resin richmaterial.

The outside wear skirt would then continue to be cast up to the top andthe O ring face 22 would be overcast in the same way as was describedfor face 15 in FIG. 30.

Disc 23 would serve to locate the top of the lost wax piece 20.

Once initial curing has occurred the outer split casing can be removedand then the whole unit can then be post cured. This post cure would befirstly at a temperature below the melting point of the wax and thenonce it is fully cured at this temperature, at about 180° C. or asrequired. During this second cure, the wax would melt out leaving ring19 free to be removed and reused.

FIG. 32 shows, for comparison, a single removable casing piece 34 on theleft hand side of the Figure, relative to a multiple stacked casing ringassembly 8 on the right Also, on the left, the necessary tapered flowprofile is created by keeping the core piece (9) profiles constant overthe height of the unit and tapering in the casing 34. The amount oftaper which can be created on the outside of the unit is clearlydemonstrated by the width of the elastomeric ring 35 on the leftrelative to that which would be needed for the right hand arrangement.

On the right hand side of FIG. 32, the necessary taper is created bykeeping the casing rings 8 constant and having variable sized corepieces 9 and 10. With this right handed arrangement, the IGCP units haveto be assembled and taken apart on the basis of one core, one casingring, one core, one casing ring, etc. However in this detail, the singlecasing 34 can be slid over the central core. This enables cleaning,scale removal and wear assessment to be simplified.

Whilst it is not shown here when the casting techniques referred to insection 5.3 are exploited, the wear ring 19 can be made integral withthe spinner skirt section 13.

It will be appreciated that many variations in detail are possiblewithout departing from the scope or spirit of the invention as claimedin the claims herein after, such as the application of the method andequipment to other off-gases and dust emissions.

1. Equipment for use in the removal of at least one of relatively fineparticulates and components from a first substance, using a secondsubstance, the equipment including a static, co-current contacting mixersection having a plurality of stages defining a flow path, with a flowprofile, for the first and the second substance, at least one stagebeing shaped to define a substantially curved flow path section havingan effective centre of curvature located to one side of the flow path,an outside surface and an inside surface between the outside surface andthe centre of curvature; at least one immediately adjacent stage beingshaped to define an oppositely curved flow path section having a centreof curvature on an opposite side of the flow path, an outside surfaceand an inside surface between the outside surface and the centre ofcurvature whereby, as the first and second substances flow through themixer section, the second substance and particles present in the firstsubstance migrate through the first substance, first in one directionrelative to a general flow direction and then in a substantiallyopposite direction to promote interphasic interaction, the flow pathcharacterised in being provided with an edge formation in a regionbetween said adjacent stages so as to enhance launch of the secondsubstance on the outside surface of the curved flow path section of saidat least one stage towards the outside surface of the oppositely curvedflow path section of the immediately adjacent stage, thus increasing theinterphasic interaction.
 2. Equipment as claimed in claim 1 wherein thefirst substance is a gas and the second substance is a scrubbing fluid.3. Equipment as claimed in claim 2 wherein the edge formation isstepped, with a substantially perpendicular face relative to the edgeformation to enhance the launch of the scrubbing fluid.
 4. Equipment asclaimed in claim 3 wherein the stepped edge formation is provided with aledge subsequent to the step to define a first and a second step, thefirst and the second step being arranged so as to encourage a small backeddy of gas immediately beneath the first step that deflects anydownwards dribble of scrubbing fluid around the stepped edge back upinto an underside of the main fluid flow as it leaves the first step soas to enhance the contact between the launched fluid and the gas. 5.Equipment as claimed in claim 4 wherein the edge formation defines afillet radius between the perpendicular face and the ledge to ensuremaximum effect from the back eddy.
 6. Equipment as claimed in claim 4 orclaim 5 wherein the length of the perpendicular face is similar to thelength of the ledge.
 7. Equipment as claimed in claim 1 wherein themixer comprises a plurality of adjacent stages with oppositely curvedflow path sections and wherein an edge formation is provided betweeneach of such adjacent stages.
 8. Equipment as claimed in claim 7 whereinthe flow path is configured and dimensioned to orientate both the angleand the position of each launch with respect to the subsequent shape ofthe flow profile and to the controlled change in direction of the flowprofile so as to catch the maximum of the scrubbing fluid that islaunched at a landing zone on the opposite side of the flow profilebefore a subsequent launch so as to enhance the scrubbing effect fromthe bulk of the scrubbing fluid.
 9. Equipment as claimed in claim 8wherein the flow path has a flow profile that is configured anddimensioned, with a step towards the start of each inside radius, suchthat the position of launch of effectively the bulk of the scrubbingfluid is towards the beginning of each inside curve so as to enhance thecontact between the launched scrubbing fluid and the gas.
 10. Equipmentas claimed in claim 2 wherein the flow path has a flow profile that isconfigured and dimensioned such that the scrubbing fluid leaves at thepoint of launch as a substantially single, flat layer of fluid, therebyensuring that the minimum of droplets are released within the shadow ofdroplets that left prior thereto so as to maximize the contact betweenthe launched fluid and the gas.
 11. Equipment as claimed in claim 2wherein the flow path has a flow profile that is configured anddimensioned such that the bulk of the scrubbing fluid reaches the farside of the flow profile before the scrubbing fluid on that side isreleased at the position of launch towards the beginning of the nextbend so as to maximize the contact between the launched scrubbing fluidand the gas.
 12. Equipment as claimed in claim 3 wherein the flow pathhas a flow profile that is configured and dimensioned such that, by theangle of the lead up to that step and the introduction of substantiallyaxially orientated straight sections to the flow profiles, the scrubbingfluid, when reaching the opposite side wall, arrives at an angle ofapproach which approaches zero degrees so as to maximise the recovery ofthe energy of the droplets within the surface film and therefore tominimise abrasion at the landing zone.
 13. Equipment as claimed in claim3 wherein the flow path has a flow profile that is configured anddimensioned, by the introduction of substantially axially orientatedstraight sections to the flow profiles, so that the distance from thelanding zone to the subsequent launching point is reduced so as tominimise the subsequent effects of viscous drag on the landing velocityof the fluid.
 14. Equipment as claimed in claim 3 wherein the flow pathhas an increased launch angle of between about 3° and 10° relative tothat which is used for the outer annulus.
 15. Equipment as claimed inclaim 3 wherein the flow path is configured and dimensioned to providean increased gas velocity down the inner annulus of between about 5 and25% relative to that down the outer annulus.
 16. Equipment as claimed inclaim 3 wherein the flow path has a flow profile that is characterisedin that the bend that gathers the scrubbing fluid ready for launchinginto the outer annulus is configured and dimensioned such that thescrubbing fluid droplet impingement and film velocity on this bend andat the subsequent launch point are no more severe than for that at theequivalent point in the outer annulus.
 17. Equipment as claimed in claim3 wherein the flow path has a flow profile that is configured anddimensioned such that the section of the flow profile leading from eachinner annular zone to the respective following outer annular zoneoptimises recovery of the extra velocity energy in the inner annulusarea back to pressure energy at the outer annulus.
 18. Equipment asclaimed in claim 3 wherein the flow path has a flow profile downstreamof the landing zone for the bulk of the droplets wherein the flow areaincreases substantially steadily and progressively whilst maintaining arelatively constant flow direction and achieving a substantial portionof the flow area of the outer annulus prior to the outer annulus launchpoint and prior to the associated change in direction of the gas flow.19. Equipment as claimed in claim 3 wherein the mixer section ischaracterized in achieving removal efficiencies of above 90% of particlesizes of less than 0.05 micron.
 20. Equipment as claimed in claim 2wherein the gas is waste gas from a modern high-performance SinterPlant.
 21. Equipment as claimed in claim 2 wherein the mixer section isprovided with a scrubbing fluid inlet, the scrubbing fluid inlet beingconfigured and dimensioned to create relative adiabatic quenching of thegases.
 22. Equipment as claimed in claim 21 wherein the adiabaticquenching of the gases is to a temperature of between 20 and 60° C. 23.Equipment as claimed in claim 22 wherein the adiabatic quenching of thegases is to a temperature of about 30 to 50° C.
 24. Equipment as claimedin claim 2 wherein the scrubbing fluid inlet is arranged such that thebulk of the scrubbing fluid retains a large droplet form and a lowlaunch velocity relative to the droplet sizes and launch velocities inthe subsequent stages in the mixer section.
 25. Equipment as claimed inclaim 2 including a cyclonic section for the separation of the gas andthe scrubbing fluid.
 26. Equipment as claimed in claim 25 wherein thecyclonic section fits substantially within the same cylindrical profileas that of the mixer section.
 27. Equipment as claimed in claim 26wherein the outlet for the scrubbing fluid is connected in an axialdirection and substantially within the same overall cylindrical profile.28. Equipment as claimed in claim 25 wherein the cyclonic section isprovided with an exit end in the form of a vortex finder configured anddimensioned to duct away the main vortex of the substantially scrubbingfluid free gas while gathering the substantially gas free scrubbingfluid off the wall of the cyclonic section.
 29. Equipment as claimed inclaim 25 characterized in having a cyclonic section of predeterminedlength in order to retain the radial velocity component of the gas flowwithin the cyclone body within a range required to get the requireddegree of separation of scrubbing fluid droplets prior to dischargingthe gas.
 30. Equipment as claimed in claim 29 wherein the distancebetween the spinner section and the top of the vortex finder is about 5to 10 times the diameter of the cyclonic section.
 31. Equipment asclaimed in claim 30 wherein the cyclonic section has a length of about1.5 to 2.5 metres and a diameter of about 0.1 to 0.5 metres. 32.Equipment as claimed in claim 31 wherein the cyclonic section has alength of about 2 metres and a diameter of about 0.3 metres. 33.Equipment as claimed in claim 2 including a spinner section, having aset of angled blades for imparting a circulatory motion to the gas andscrubbing fluid mixture prior to entry of the cyclonic section. 34.Equipment as claimed in claim 33 wherein the width of the flow paththrough the spinner section is increased radially so that the crosssectional area for the flow is maintained relatively constant as theflow direction changes, thus retaining relative exit velocities of thegas and the scrubbing fluid substantially similar to the respectiveentry velocities.
 35. Equipment as claimed in claim 33 wherein thespinner section is configured and dimensioned so that any object thatcan pass through the main mixer section can also pass through thespinner section.
 36. Equipment as claimed in claim 33 wherein thespinner section is provided with an annulus through which the gases andscrubbing fluid flow so as to calm the bulk of any residual turbulencefrom the spinner blades.
 37. Equipment as claimed in claim 36 whereinthe annulus has an inner, substantially hollow profile with acylindrical recess with a suitably shaped inner end in order to removedroplets of scrubbing fluid that contaminate the scrubbed and cyclonedproduct gases.
 38. Equipment as claimed in claim 3 including a centrallyorientated, discharge pipe relatively to the vortex finder, with adiameter of about 70 to 90% of that of the vortex finder outlet,providing an annular gap there between.
 39. Equipment as claimed inclaim 38 wherein the annular gap is configured and dimensioned to passdebris that could access the equipment and wider than the typicalmaximum splash and spray layer that would accompany the scrubbing fluidas it runs down the inner walls of the cyclonic section.
 40. Equipmentas claimed in claim 33 wherein the gap is configured and dimensioned sothat the minimum width of the annular gap at the vortex finder is basedon the concept of capturing all the splash and spray into this annulararea.
 41. Equipment as claimed in claim 33 wherein the mixer section,the spinner section and the cyclonic section are cast in a single,substantially integral unit.
 42. A method for the removal of at leastone of relatively fine particulates and components from a firstsubstance, using a second substance, the method including the steps oftransporting the first substance and the second substance through aplurality of stages defining a flow path, at least one of the stagesbeing shaped to define a substantially curved flow path section havingan effective centre of curvature located to one side of the flow path,an outside surface and an inside surface between the outside surface andthe centre of curvature; at least one immediately adjacent stage beingshaped to define an oppositely curved flow path section having a centreof curvature on an opposite side of the flow path, an outside surfaceand an inside surface between the outside surface and the centre ofcurvature, whereby as the first substance and the second substance flowthrough the flow path the second substance and particles present in thefirst substance migrate through the first substance, first in onedirection and then in a substantially opposite direction to promoteinterphasic interaction; and utilizing a launch formation between theadjacent stages for launching the second substance on the outsidesurface of the curved flow path section of the at least one stage to theoutside surface of the curved flow path section of the immediatelyadjacent stage, to increase the interphasic interaction.
 43. A method asclaimed in claim 42 wherein the first substance is a gas and the secondsubstance is a scrubbing fluid.
 44. A method as claimed in claim 42characterized in achieving removal efficiencies of above 90% of particlesizes of less than 0.05 micron.
 45. A method as claimed in claim 43characterized in being suitable for scrubbing waste gas from a modernhigh-performance Sinter Plant, using a suitable scrubbing fluid.
 46. Amethod as claimed in claim 43 including the step of adding a relativelyfine dust upstream of the mixer section to enhance the removal ofvapours in the gas.
 47. A method as claimed in claim 46 wherein the finedust is pre-selected so as to enhance the chemisorbtion on to the dustof gasses and vapours selected from the group consisting of dibenzofuran, PCB, related compounds and any combinations thereof. 48-59.(canceled)